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Symbiotic bacteria often navigate complex environments before colonizing privileged sites in their host organism. Chemical gradients are known to facilitate directional taxis of these bacteria, guiding them towards their eventual destination. However, less is known about the role of physical features in shaping the path the bacteria take and defining how they traverse a given space. The flagellated marine bacteriumVibrio fischeri,which forms a binary symbiosis with the Hawaiian bobtail squid,Euprymna scolopes, must navigate tight physical confinement, squeezing through a bottleneck constricting to ~2 μm in width on the way to its eventual home. Using microfluidicin vitroexperiments, we discovered thatV. fischericells alter their behavior upon entry into confined space, straightening their swimming paths and promoting escape from confinement. Using a computational model, we attributed this escape response to two factors: reduced directional fluctuation and a refractory period between reversals. Additional experiments in asymmetric capillary tubes confirmed thatV. fischeriquickly escape from tapered ends, even when drawn into the ends by chemoattraction. This avoidance was apparent down to a limit of confinement approaching the diameter of the cell itself, resulting in a balance between chemoattraction and evasion of physical confinement. Our findings demonstrate that non-trivial distributions of swimming bacteria can emerge from simple physical gradients in the level of confinement. Tight spaces may serve as an additional, crucial cue for bacteria while they navigate complex environments to enter specific habitats.Significance StatementSymbiotic bacteria that navigate to and through specific host tissues often face tight physical confinement. This work reveals that confinement-associated changes in swimming can dramatically alter taxis, shaping bacterial localization in conjuncture with other motility-directing cues. This work helps explain how bacteria can avoid getting stuck in confined areas while transiting to privileged spaces, adding confinement as an environmental cue that symbiotic bacteria use to shape their motility behavior.

Bacterial symbionts of insects have been shown to play important roles in host fitness. However, little is known about the bacterial community of Tessaratoma papillosa which is one of the most destructive pests of the well-known fruits Litchi chinensis Sonn and Dimocarpus longan Lour in Oriental Region, especially in South-east Asia and adjacent areas. In this study, we surveyed the bacterial community diversity and dynamics of T. papillosa in all developmental stages with both culture-dependent and culture-independent methods by the third-generation sequencing technology. Five bacterial phyla were identified in seven developmental stages of T. papillosa. Proteobacteria was the dominant phylum and Pantoea was the dominant genus of T. papillosa. The results of alpha and beta diversity analyses showed that egg stage had the most complex bacterial community. Some of different developmental stages showed similarities, which were clustered into three phases: (1) egg stage, (2) early nymph stages (instars 1-3), and (3) late nymph stages (instars 4-5) and adult stage. Functional prediction indicated that the bacterial community played different roles in these three phases. Furthermore, 109 different bacterial strains were isolated and identified from various developmental stages. This study revealed the relationship between the symbiotic bacteria and the development of T. papillosa, and may thus contribute to the biological control techniques of T. papillosa in the future.

Background Shipworms are marine xylophagus bivalve molluscs, which can live on a diet solely of wood due to their ability to produce plant cell wall-degrading enzymes. Bacterial carbohydrate-active enzymes (CAZymes), synthesised by endosymbionts living in specialised shipworm cells called bacteriocytes and located in the animal’s gills, play an important role in wood digestion in shipworms. However, the main site of lignocellulose digestion within these wood-boring molluscs, which contains both endogenous lignocellulolytic enzymes and prokaryotic enzymes, is the caecum, and the mechanism by which bacterial enzymes reach the distant caecum lumen has remained so far mysterious. Here, we provide a characterisation of the path through which bacterial CAZymes produced in the gills of the shipworm Lyrodus pedicellatus reach the distant caecum to contribute to the digestion of wood. Results Through a combination of transcriptomics, proteomics, X-ray microtomography, electron microscopy studies and in vitro biochemical characterisation, we show that wood-digesting enzymes produced by symbiotic bacteria are localised not only in the gills, but also in the lumen of the food groove, a stream of mucus secreted by gill cells that carries food particles trapped by filter feeding to the mouth. Bacterial CAZymes are also present in the crystalline style and in the caecum of their shipworm host, suggesting a unique pathway by which enzymes involved in a symbiotic interaction are transported to their site of action. Finally, we characterise in vitro four new bacterial glycosyl hydrolases and a lytic polysaccharide monooxygenase identified in our transcriptomic and proteomic analyses as some of the major bacterial enzymes involved in this unusual biological system. Conclusion Based on our data, we propose that bacteria and their enzymes are transported from the gills along the food groove to the shipworm’s mouth and digestive tract, where they aid in wood digestion.

The melon fly, Zeugodacus cucurbitae (Diptera:Tephritidae) is one of the devastating pests of most cucurbits in India and its management by application of synthetic insecticides remained unsuccessful. Tephritid fruit flies are reported to harbour symbiotic microbiota in their gut and ovipositor, providing them nutritional resources in the ecosystem. The current study was carried out to isolate the symbionts and to test their attraction potential for trapping the melon fly adults. From the molecular analysis of 16S rRNA gene, 11 different species of bacteria were identified from gut and ovipositor of wild population of melon fruit fly. Among the identified bacteria, 7 species belonged to Enterobacteriaceae family, 2 species belonged to Bacillaceae family and one each belonged to Enterococcaceae and Flavobacteriaceae family. Among them Enterococcus faecalis, Citrobacter sp., E. meningoseptica, Klebsiella oxytoca, Bacillus amyloliquefaciens and Bacillus sp. were found only in ovipositor of the flies. Whereas, Raoultella ornithinolytica and Klebsiella sp. were found only in gut of the fruit flies. Two bacterial species, namely K. pneumoniae and E. cloacae were identified from both ovipositor and gut of wild flies. Five volatiles identified from these two bacteria were ammonia, dimethyl disulphide, methoxy phenyl oxime, 2, 2-dihydroxy-1-phenyl ethanone and butyl-2-methylpropyl ester of 1, 2-benzenedicarboxylic acid. The synthetic forms of identified volatiles and related compounds were tested for their potential to attract melon fruit fly. Ammonium hydroxide showed maximum attraction followed by iso amyl alcohol and dimethyl disulphide. Among the flies, 0–2 days old and 6–8 days old adults showed slightly higher attractancy towards the volatiles compared to 20–30 days old adults. Protein fed and protein starved adults showed maximum attractancy towards Ammonium hydroxide followed by Iso amyl alcohol. All the volatiles attracted more female flies compared to male flies.

Nutritional mutualism between insects and symbiotic bacteria is widespread. The various sap-feeding whitefly species within the Bemisia tabaci complex associate with the same obligate symbiont (Portiera) and multiple secondary symbionts. It is often assumed that some of the symbionts residing in the whiteflies play crucial roles in the nutritional physiology of their insect hosts. Although effort has been made to understand the functions of the whitefly symbionts, the metabolic complementarity offered by these symbionts to the hosts is not yet well understood. We examined two secondary symbionts, Arsenophonus and Wolbachia, in two species of the B. tabaci whitefly complex, provisionally named as Asia II 3 and China 1. Genomic sequence analyses revealed that Arsenophonus and Wolbachia retained genes responsible for the biosynthesis of B vitamins. We then conducted transcriptomic surveys of the bacteriomes in these two species of whiteflies together with that in another species named MED of this whitefly complex previously reported. The analyses indicated that several key genes in B vitamin syntheses from the three whitefly species were identical. Our findings suggest that, similar to another secondary symbiont Hamiltonella, Arsenophonus and Wolbachia function in the nutrient provision of host whiteflies. Although phylogenetically distant species of symbionts are associated with their respective hosts, they have evolved and retained similar functions in biosynthesis of some B vitamins. Such metabolic complementarity between whiteflies and symbionts represents an important feature of their coevolution.

It is well concluded that microbial composition and diversity of coral species can be affected under temperature alterations. However, the interaction of environmental accumulation of corals and temperature stress on symbiotic Symbiodiniaceae and bacterial communities are rarely studied. In this study, two groups of soft coral Sarcophyton trocheliophorum were cultured under constant (26 °C) and inconstant (22 °C to 26 °C) temperature conditions for 30 days as control treatments. After that, water was cooled rapidly to decrease to 20 °C in 24 h. The results of diversity analysis showed that symbiotic Symbiodiniaceae and bacterial communities had a significant difference between the two accumulated groups. The principal coordinate analyses confirmed that symbiotic Symbiodiniaceae and bacterial communities of both control treatments were clustered into two groups. Our results evidenced that rapid cooling stress could not change symbiotic Symbiodiniaceae and bacterial communities’ composition. On the other hand, cooling stress could alter only bacterial communities in constant group. In conclusion, our study represents a clear relationship between environmental accumulation and the impact of short-term cooling stress in which microbial composition structure can be affected by early adaptation conditions.

Complex interactions between symbiotic bacteria and insects ultimately result in equilibrium in all aspects of life in natural insect populations. In this study, abundance of principal symbiotic bacteria was estimated using qPCR in 1553 individuals of aphids, Aphis gossypii. Aphids were sampled from primary and secondary host plants—hibiscus and cotton. Hibiscus aphids were collected from 24 different locations in April, September, and November, whereas cotton aphids were collected between 2015 and 2017 from areas with wide variations in climatic conditions. About 30%–45% aphids were recorded with the most dominant symbiont, Arsenophonus. The other symbionts were in low frequency, and about 7% of aphids were noted with Hamiltonella, Acinetobacter, and Microbacterium, and 3% of aphids were verified with Serratia and Pseudomonas. Aphids infected with Hamiltonella, Arsenophonus, and Serratia can influence Buchnera densities. Hamiltonella has positive interaction with densities of Arsenophonus and Serratia. Almost 100% coinfection of Hamiltonella and Arsenophonus was detected in Xinxiang aphids and 50% coinfection was reported in aphids from North China, while no coinfection was detected in Hainan aphids. These findings describe the prevalence pattern and richness of core community of symbiotic bacteria in naturally occurring populations of A. gossypii and provide new insights for the study of symbiotic bacteria.

The appearance and rapid spread of new invasive leafhopper species Metcalfa pruinosa (Say, 1830) and Arboridia kakogawana (Matsumura, 1932) in Russia requires studying both the causes of the invasion and consequences of invasion for viticulture. Of particular interest is the study of the possible role of new species of leafhoppers in the spread of pathogenic bacteria of grape phytoplasmosis. At present, these issues are poorly studied. We characterized the variability of the BOLD fragment of the mitochondrial COI gene in the population samples of M. pruinosa and A. kakogawana from the populations of Crimea and the Black Sea coast of the Caucasus. With the help of PCR for specific genes, we searched for leafhoppers infected with bacteria of phytoplasmosis of grapes from the group of stolbur (Candidatus Phytoplasma solani) and intracellular symbiotic bacteria: Wolbachia, Rickettsia, and Spiroplasma. We found M. pruinosa only on the Black Sea coast of the Caucasus. The M. pruinosa populations are close to monomorphism. We found A. kakogawana in both Crimea and the Caucasus region. We have identified two new forms of this species in Russia. We have not found pathogenic bacteria of phytoplasmosis of grapes and intracellular symbiotic bacteria in studied leafhopper populations.

Since the outset of the coronavirus disease 2019 (COVID-19) pandemic, the gut microbiome in COVID-19 has garnered substantial interest, given its significant roles in human health and pathophysiology. Accumulating evidence is unveiling that the gut microbiome is broadly altered in COVID-19, including the bacterial microbiome, mycobiome, and virome. Overall, the gut microbial ecological network is significantly weakened and becomes sparse in patients with COVID-19, together with a decrease in gut microbiome diversity. Beyond the existence of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), the gut microbiome of patients with COVID-19 is also characterized by enrichment of opportunistic bacteria, fungi, and eukaryotic viruses, which are also associated with disease severity and presentation. Meanwhile, a multitude of symbiotic bacteria and bacteriophages are decreased in abundance in patients with COVID-19. Such gut microbiome features persist in a significant subset of patients with COVID-19 even after disease resolution, coinciding with ‘long COVID’ (also known as post-acute sequelae of COVID-19). The broadly-altered gut microbiome is largely a consequence of SARS-CoV-2 infection and its downstream detrimental effects on the systemic host immunity and the gut milieu. The impaired host immunity and distorted gut microbial ecology, particularly loss of low-abundance beneficial bacteria and blooms of opportunistic fungi including Candida, may hinder the re-assembly of the gut microbiome post COVID-19. Future investigation is necessary to fully understand the role of the gut microbiome in host immunity against SARS-CoV-2 infection, as well as the long-term effect of COVID-19 on the gut microbiome in relation to the host health after the pandemic.

Soil inhabiting organisms are important determinants of agroecosystem productivity. Understanding the composition, the abundance, and the type of interactions established by soil microorganisms is therefore crucial to design strategies to improve agricultural practices and agroecosystem management. In this study, we collected Zeldia punctata nematodes in maize fields in South Africa and profiled their associated bacterial communities using next-generation sequencing. We observed that Z. punctata nematodes establish associations with ecologically diverse bacterial species. The most abundant species observed are Pseudomonas syringae, a phytopathogenic bacterial complex; Lactobacillus paraplantarum, a broadly distributed bacterial species that is present in soils, water bodies, and animal intestinal tracts and has certain probiotic and antimicrobial properties; and Melissococcus plutonius, a serious pathogenic bacterial species that causes brood disease in honeybees. Our study contributes to a better understanding of the soil bacterial communities associated with nematodes in maize agricultural soils in South Africa and unravels the presence of diverse detrimental and beneficial nematode-associated bacteria.

Summary Entomopathogenic nematodes (EPN) Steinernema and Heterorhabditis with symbionts with Xenorhabdus and Photorhabdus bacteria, respectively, are reported as biocontrol agents for insect control. The objectives of this study were to identify EPN and their symbiotic bacteria in national parks of Phitsanulok Province, Thailand, and to test how Xenorhabdus isolates attack Aedes aegypti larvae. We collected 810 soil samples from four national parks. The juvenile stage of EPN was isolated from soil samples using a baiting technique with Galleria mellonella followed by a White trap. Partial regions of 28S rDNA and internal transcript spacer were sequenced to identify EPN, and recA sequencing was used to discriminate between Xenorhabdus and Photorhabdus. We found that 74 of the 810 soil samples (9.1%) were positive for the EPN. The EPN were molecularly identified as S. surkhetense, S. longicaudum, H. indica and Heterorhabditis sp. SGmg3, and their symbiotic bacteria were identified as X. stockiae, X. griffiniae, X. indica, X. vietnamensis, P. luminescens subsp. akhurstii, and P. temperata subsp. temperata. Xenorhabdus griffiniae showed potential larvicidal activity against A. aegypti (91% mortality at 72 and 96 h after exposure). This study demonstrates the diversity of EPN and symbiotic bacteria in national parks of Thailand and the potential to use X. griffiniae as a biocontrol agent to kill A. aegypti larvae.

Third and fourth instar larvae of Aedes aegypti actively ingested entomopathogenic nematodes (EPNs) and their symbiotic bacteria, resulting in larval mortality. All six EPN species evaluated in this study were pathogenic to Ae. aegypti but varied significantly in their virulence. Heterorhabditis bacteriophora and Steinernema carpocapsae were most virulent, H. megidis and S. kraussei showed the least virulence, whereas H. downesi and S. feltiae had intermediate virulence. Larval mortality was dose dependent for all EPN species. When using a dose of 100 infective juveniles (IJs) per larva, H. bacteriophora and S. carpocapsae caused 90%-100% mortality, whereas H. downesi and S. feltiae caused only 40%-60% mortality. Even when using 200 IJs/larva, H. megidis and S. kraussei caused a maximum of 30%-40% mortality. Some of the invasive EPNs were melanized, suggesting a strong humoral defense response by the Aedes larvae. The degree of melanization was quite variable; some EPNs were totally enveloped in a melanin sheath while others were partially coated with melanin. Melanization did not stop the EPN from multiplying and killing the Aedes larvae. IJs released from infected larvae would have the potential to infect healthy mosquito larvae. Also, both bacterial supernatant and bacterial cell suspension of Xenorhabdus nematophila caused >91% larval mortality after 48 h, whereas only the bacterial cell suspension of Photorhabdus laumondii was effective against the mosquito larvae. These data provides useful information on the potential use of EPNs and/or formulated bacterial cell suspensions in the control of the important urban and container-breeding mosquito, Ae. aegypti, and are a starting point for future simulated and actual field studies.

Entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema kill insects with the help of their symbiotic bacteria. They are widely used as biocontrol agents to manage insect pests of crops. The infective juveniles (IJ) of EPNs are isolated from soil by insect baiting technique, which is labour-intensive, time-consuming, wasteful, and inefficient. Here, we present loop-mediated isothermal amplification (LAMP) assays for rapid detection of Heterorhabditis spp. (Het-LAMP) and Steinernema spp. (Ste-LAMP) from total soil DNA. The primers for Het-LAMP and Ste-LAMP were designed using ITS and 18S rDNA regions of genomic DNA. The LAMP reactions could be completed in 60 min, at 66 °C and 68 °C, respectively, followed by termination at 85 °C for 5 min. The assays were highly sensitive and could detect up to 0.02 picograms of Heterorhabditis DNA and 96 picograms of Steinernema DNA in a 25 μl reaction. Both the assays were specific for the target nematode species and detected the presence of a single IJ in the total DNA extracted from 250 mg of soil. The assays developed in this study would be of immense utility for the efficient detection and identification of native EPNs in large-scale surveys. These assays are amenable to automation and could be used to develop convenient detection kits for point-of-service diagnosis of EPNs in the field without the need for a trained and experienced personnel.

Black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), larvae are suspected to inhibit house flies, Musca domestica (L.) (Diptera: Muscidae), seeking oviposition sites. However, the mechanisms regulating these interactions are not well known. In this study, a Y-tube olfactometer was used to determine whether black soldier fly eggs, larvae, puparia (without pupae inside), adult carcasses, or resulting frass of black soldier fly decrease attractiveness of adult house flies to an oviposition substrate (i.e., sugar and wheat bran diet, used as the control). Secondly, two symbiotic bacteria associated were isolated, identified, and tested for house fly attractiveness with a Y-tube olfactometer. Thirdly, volatile organic compounds produced by swine feed before and after black soldier fly, or house fly larval digestion were analyzed with gas chromatography–mass spectrometry (GC–MS). Results indicate feed mixed with black soldier fly larval frass, and symbiotic bacteria, Paenalcaligenes sp. associated with black soldier fly, were less attractive to house flies than the control. However, another symbiotic bacterium Lysinibacillus sp. associated with black soldier fly pupae was attractive. In total, 52 volatile organic compounds were identified from treatments previously described. Quantitative differences in volatile profiles across treatments potentially explain the mechanism regulating house fly substrate choices in the presence, or absence, of black soldier fly larvae.

The first results of a study into the microbiomes of benthic invertebrates found in sites with seeps (containing methane, oil, or a combination of methane and mud) and an underwater low-temperature vent of Lake Baikal are presented. Microorganisms were detected in the intestine of an oligochaete from the cold methane seep using microscopy. Analysis of 16S rRNA gene libraries revealed that the highest diversity of microorganisms was found in the nematode microbiomes where the members of 11 phyla were identified. Some of the detected prokaryotes are methanogens, nitrifiers, and nitrogen fixators, while some are involved in the sulfur cycle. Methanotrophs were detected in the microbiomes of oligochaetes and chironomids. The microbiomes of nematodes, chironomids, and bathynellids are composed of members of the Bacteroidetes and Firmicutes phyla, which are related to the symbiotic bacteria found in insects and animals from other ecotopes. Microorganisms typically found in the water and sediments of Lake Baikal were also detected in the invertebrates microbiomes.

The cabbage butterfly (Pieris brassicae L.) is a major insect pest of cabbage in Pakistan. Heterorhabditis bacteriophora (at 1500 infective juvenile/ ml concentraction), Steinerma glaseri (at 1500 infective juvenile/ ml concentration), H. bacteriophora + S. glaseri (at 1500 infective juvenile/ ml concentration), Xenorhabdus spp., (at 4 × 1012 concentration) Photorhabdus spp., (at 4 × 1012 concentration) metabolites of Xenorhabdus spp. (at 50% concentration) and metabolites of Photorhabdus spp (at 50% concentration) were sprayed on cabbage hybrid CB-60 grown in pots placed in the greenhouse. After 7 days, the highest P. brassicae larval mortality (90.43%) was observed where H. bacteriophora + S. glaseri were sprayed. In field experiment, best-performing treatments from greenhouse experiment were selected i.e. H. bacteriophora + S. glaseri (at 1500 infective juvenile/ ml concentration), Xenorhabdus spp., (at 4 × 1012 concentration) and metabolites of Xenorhabdus spp. (at 50% concentration) were sprayed on a highly susceptible cabbage hybrid (CB-60). Heterorhabditis bacteriophora + Steinerma. glaseri @ 1500 infective juvenile/ ml was found to be more superior with maximum mortality (80.43) of cabbage butterfly larvae in comparison with other treatments. From the present study, it may be concluded that EPNs (H. bacteriophora and S. glaseri) application is more effective as compared to their symbiotic bacteria and metabolite for cabbage butterfly management.

For more than 30 years, the association between the Hawaiian bobtail squid, Euprymna scolopes, and the bioluminescent bacterium Vibrio fischeri has been studied as a model system for understanding the colonization of animal epithelia by symbiotic bacteria. The squid–vibrio light-organ system provides the exquisite resolution only possible with the study of a binary partnership. The impact of this relationship on the partners’ biology has been broadly characterized, including their ecology and evolutionary biology as well as the underlying molecular mechanisms of symbiotic dynamics. Much has been learned about the factors that foster initial light-organ colonization, and more recently about the maturation and long-term maintenance of the association. This Review synthesizes the results of recent research on the light-organ association and also describes the development of new horizons for E. scolopes as a model organism that promises to inform biology and biomedicine about the basic nature of host–microorganism interactions. In this Review Nyholm and McFall-Ngai describe recent advances in understanding the squid–vibrio symbiosis, specifically the strides that have been made in recent years in the study of bobtail squid symbiosis from the host viewpoint.

Marine organism is one of the riches in the ocean of Indonesia. The benefits of sea use for new products produced are widely used and have high market demand. Enzymes that have marine interests have unique properties and have good benefits for industry. This study aims to isolate the bacteria that have symbionts with Padina sp and determine the potential of the enzyme hydrolase produced by these bacteria. Isolation is done by the spread plate method. Pure isolates obtained were then tested for the potential of the enzyme hydrolase on selective media. Clear zone measurements are performed to determine which bacterial isolates are good for enzyme production. The results obtained by 6 isolates of pure bacteria, all of which include Gram negative bacteria that form bacilli. All isolates had the ability to produce different Protease, Lipase, Amylase and Cellulase enzymes. The enzymes obtained from these symbiotic bacteria are expected to be used for industrial-scale production in Indonesia. In addition, the presence of this symbiont bacteria is able to reduce the level of exploitation of Padina sp and contribute to preserving the marine ecosystem.

Summary Deep‐sea hydrothermal vents harbour diverse and abundant animals and their symbiotic microorganisms, which together comprise holobionts. The interplay between bacterial members of holobionts and their viruses (phages) is important for maintaining these symbiotic systems; however, phage–bacterium interactions in deep‐sea vent holobionts are not well understood. Marine sponges serve as good models for such studies and are used to unveil phage–bacterium interplay via metagenomic analysis. In three demosponges from deep‐sea hydrothermal vent fields in the southern Okinawa Trough, the genomes of a diverse array of symbiotic bacteria, including 10 bacterial phyla, were found to lack intact prophages. Genes related to diverse anti‐viral defence systems, for example, the restriction–modification and toxin–antitoxin systems, were abundant in the bacterial communities. We also detected phage genes that could complement or compensate host bacterial metabolism, indicating beneficial roles of phage infection. Our findings provide insight into phage–bacterium interplay in sponges from deep‐sea hydrothermal vents.

Entomopathogenic nematodes (EPN) are one of the soil worms that have been widely used as a natural pest control. EPN has its pathogenic capability because of the mutualistic interactions between nematodes and symbiotic bacteria inside the digestive tract of nematodes. Symbiotic bacteria capable of producing exoenzymes that are toxic to insects. The isolation of symbiotic bacteria accomplished by infection of obtained EPN (Belik II isolate) into Tenebrio molitor larvae. Symbiotic bacteria were isolated from the hemolymph of dead larvae on NBTA media. Isolation of symbiotic bacteria was successfully obtained two morphologically distinct bacteria: B 3.1 isolate and B 4 isolate. Both bacteria were further identified using PCR analysis of the 16S rRNA gene. Based on the sequencing results, the B 3.1 isolate was in accordance with Acinetobacter pittii strain ATCC 19004, while B 4 isolate was in accordance with bacteria Enterobacter aerogenes strain KCTC 2190. The characterization of B 3.1 isolate was shown to have similarities with Acinetobacter sp., i.e.: gram-negative, non - motile, rod-shaped, and some other characteristics of biochemical tests. While the characterization of B 4 isolate was shown to have similarities with E. aerogenes i.e.: gram-negative, rod-shaped, motile, and some other characteristics of biochemical tests. These findings will be the potential to be applied as biological agents in pest control.

The Black-veined White Aporia crataegi (Lepidoptera: Pieridae) is a trans-Palearctic species causing damage to various fruit and berry crops. Here we analyzed Wolbachia infection in A. crataegi populations. Wolbachia bacteria are maternally transmitted intracellular symbionts of many arthropods, including numerous Lepidoptera. We have studied 376 samples of A. crataegi collected in 10 regions of Russia from the Far East to Kaliningrad. Wolbachia prevalence was very low; only eight Wolbachia-positive specimens of A. crataegi were detected in Yakutia, Republic of Buryatia, Sverdlovsk and Kaliningrad Provinces, and no infection was found in other localities. Two Wolbachia haplotypes, ST-19 and ST-109, from A and B supergroups respectively, were identified using the multilocus sequence typing (MLST) protocol. These haplotypes were also previously reported in different lepidopteran species. Both Wolbachia haplotypes were associated with the same mtDNA haplotype (as inferred from the cytochrome oxidase subunit I gene) of A. crataegi, and ST-19 with two mtDNA haplotypes. This incongruence of maternally inherited agents indicates independent cases of the bacteria acquisition in A. crataegi history. The above data suggest that Wolbachia can infect Aporia crataegi but cannot establish in the host populations.

Background Aphis gossypii, a polyphagous and recurrent pest induced by pesticides, causes tremendous loss in the yield of crops each year. Previous studies of pesticide-induced sublethal effects mechanism mainly focus on gene level. The symbiotic bacteria are also important participants of this mechanism, but their roles in hormesis are still unclear. Results In this study, life table parameters and 16S rRNA sequencing were applied to evaluate the sublethal and transgenerational effects of sulfoxaflor on adult A. gossypii after 24-h LC20 (6.96 mg L-1 ) concentration exposure. The results indicated that the LC20 of sulfoxaflor significantly reduced the finite rate of increase (λ) and net reproductive rate (R0 ) of parent generation (G0), and significantly increased mean generation time (T) of G1 and G2, but not of G3 and G4. Both reproductive period and fecundity of G1 and G2 were significantly higher than those of the control. Furthermore, our sequencing data revealed that more than 95% bacterial communities were dominated by the phylum Proteobacteria, in which the maximum proportion genus was the primary symbiont Buchnera and the facultative symbiont Arsenophonus. Compared to those of the control, the abundance and composition of symbiotic bacteria of A. gossypii for three successive generations (G0-G2) were changed after G0 A. gossypii was exposed to sulfoxaflor: the diversity of the bacterial community was decreased, but the abundance of Buchnera was increased (G0), while the abundance of Arsenophonus was decreased. Contrary to G0, G1 and G2 cotton aphid exhibited an increased relative abundance of Arsenophonus in sublethal treatment group. Conclusion Taken together, our results provide an insight into the interactions among pesticide resistance, aphids, and symbionts, which will eventually help to better manage the resurgence of A. gossypii. This article is protected by copyright. All rights reserved.

The genetically modified cotton holding Bt proteins, is noxious to bollworms larvae but very little is known about its impact on population of non-target spiders within the field. Studies conducted with the aim to identify spiders along with their abundance, prevalence pattern, preying habit on insect pests in Bt cotton (L280, Cry2Ab4) and commonness of symbiotic bacteria in these spiders. Spiders collections were made via vial tapping/jarring, from May to end of October (2018). In total, 13,342 spiders were recorded during the entire cropping season. Least relative abundance was in May (0.28%), highest in August (30.39%) while ahead decline was observed, reached to 12% in October. The 27 species were verified, least richness was in May (3 species), high in August (19 species), later in the end, reduced to 7 species. High abundance was of Hylyphantes graminicola (68.56%) and Neoscona theisi (19.98%). Existence of H. graminicola and Pardosa astrigera observed during the whole cropping season. Presence of seven guilds among spiders had a diverse nature of hunting insect pests and on number of species existed in the crop, maximum was from direct hunting habit. Composition and community structure of microbiota varied as of spider species. Proteobacteria was the most abundant bacterial phylum and topmost genus was Wolbachia in observed spiders. Five groups of bacteria distinguished across 4 clusters of spiders depending on core community of symbiotic bacterial genera. This effort is an initial step to get knowhow about spiders in Bt cotton, which will facilitate future research studies concerning spiders.

Growing evidence has highlighted the essential role of plant hormones, notably, cytokinins (CKs), in nitrogen-fixing symbiosis, both at early and late nodulation stages1,2. Despite numerous studies showing the central role of CK in nodulation, the importance of CK transport in the symbiosis is unknown. Here, we show the role of ABCG56, a full-size ATP-binding cassette (ABC) transporter in the early stages of the nodulation. MtABCG56 is expressed in roots and nodules and its messenger RNA levels increase upon treatment with symbiotic bacteria, isolated Nod factor and CKs, accumulating within the epidermis and root cortex. MtABCG56 exports bioactive CKs in an ATP-dependent manner over the plasma membrane and its disruption results in an impairment of nodulation. Our data indicate that ABCG-mediated cytokinin transport is important for proper establishment of N-fixing nodules.

Cross-kingdom interactions involve dynamic processes that shape terrestrial ecosystems and represent striking examples of co-evolution. The multifaceted relationships of entomopathogenic nematodes with their insect hosts and symbiotic bacteria are well-studied cases of co-evolution and pathogenicity. In contrast, microbial interactions in soil after the natural death of insects and other invertebrates are minimally understood. In particular, the turnover and succession of nematodes and bacteria during insect decay have not been well documented - although it represents a rich ecological niche with multiple species interactions. Here, we utilize developmentally plastic nematode Pristionchus pacificus and its associated scarab beetles as models. On La Réunion Island, we collected rhinoceros beetle Oryctes borbonicus, induced death, and placed carcasses in cages both on the island and in a mock-natural environment in the laboratory controlling for high spatial and temporal resolution. Investigating nematode population density and dispersal dynamics, we were able to connect two imperative plasticities, dauer and mouth form. We observed a biphasic 'boom and bust' dispersal dynamic of dauer larvae that corresponds to bacterial load on carcasses but not bacterial type. Strikingly, all post-dauer adults have the predatory mouth form, demonstrating novel intricate interactions on decaying insect hosts. Thus, ecologically relevant survival strategies incorporate critical plastic traits.

Helicobacter pylori infection is a major etiological factor in gastric diseases. However, clinical antibiotic therapy for H. pylori is limited by continuously decreased therapeutic efficacy and side effects to symbiotic bacteria. Herein, we develop an in vivo activatable pH-responsive graphitic nanozyme, PtCo@Graphene (PtCo@G), for selective treatment of H. pylori. Such nanozymes can resist gastric acid corrosion, exhibit oxidase-like activity to stably generate reactive oxygen species only in acidic gastric milieu and demonstrate superior selective bactericidal property. C18-PEGn-Benzeneboronic acid molecules are modified on PtCo@G, improving its targeting capability. Under acidic gastric pH, graphitic nanozymes show notable bactericidal activity toward H. pylori, while no bacterial killing is observed under intestinal conditions. In mouse model, high antibacterial capability toward H. pylori and negligible side effects toward normal tissues and symbiotic bacteria are achieved. Graphitic nanozyme displays the desired enzyme-like activities at corresponding physiological sites and may address critical issues in clinical treatment of H. pylori infections., Helicobacter pylori is a major cause of gastric diseases, but the standard therapy is limited by continuously decreased therapeutic efficacy and side effects to symbiotic bacteria. Here, the authors develop a pH-responsive graphitic nanozyme that is active under low pH gastric conditions, but inactive in intestines, for selective treatment of H. pylori infections.

Aphids are infected by a series of bacteria that can help them survive on specific host plants. However, the associations between aphids and these bacteria are not clear, and the bacterial communities in many aphid species are poorly characterized. Here, we investigated the bacterial communities of cotton aphids (Aphis gossypii) on 2 representative winter host plants and transferred to 3 summer host plants by 16S rDNA sequencing using the Illumina MiSeq platform. Our results revealed that the bacterial communities varied among cotton aphids on hibiscus, cotton aphids on pomegranate, cotton aphids on cotton transferred from hibiscus, cotton aphids on muskmelon transferred from hibiscus, cotton aphids on cucumber transferred from hibiscus,. The diversity and richness of the bacterial communities were significantly higher in aphids on muskmelon and aphids on cucumber than in the other treatments. There were two main factors influencing the distribution of internal bacterial OTUs revealed by principal component analysis, including the differences among Punicaceae, Malvaceae and Cucurbitaceae. There were 28 bacterial communities with significant differences between two arbitrary treatments, which could be grouped into 6 main clusters depending on relative abundance. Moreover, our results indicated that in addition to the obligate endosymbiont Buchnera, with a dominant position (> 52%), A. gossypii also harbored 3 facultative endosymbiotic bacteria (Serratia, Arsenophonus, and Wolbachia) and 3 possibly symbiotic bacteria (Acinetobacter, Pantoea, and Flavobacterium). There were several correspondences between the symbiotic bacteria in cotton aphids and the specific host plants of the aphids. This study provides a better understanding of the interactions among symbiotic bacteria, aphids and host plants, suggesting that the selection pressure on aphid bacterial communities is likely to be exerted by the species of host plants.

Symbiotic bacteria play vital roles in the survival and health of marine sponges. Sponges harbor rich, diverse and species-specific microbial communities. Symbiotic marine bacteria have increasingly been reported as promising source of bioactive compounds. A culturomics-based study was undertaken to study the diversity of bacteria from marine sponges and their antimicrobial potential. We have collected three sponge samples i.e. Acanthaster carteri, Rhytisma fulvum (soft coral) and Haliclona caerulea from north region (Obhur) of Red Sea, Jeddah Saudi Arabia. Total of 144 bacterial strains were isolated from three marine sponges using culture dependent method. Screening of isolated strains showed only 37 (26%) isolates as antagonists against oomycetes pathogens (P. ultimum and P. capsici). Among 37 antagonistic bacteria, only 19 bacterial strains exhibited antibacterial activity against human pathogens (Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 8739, Enterococcus faecalis ATCC 29212). Four major classes of bacteria i.e γ-Proteobacteria, α-Proteobacteria, Firmicutes and Actinobacteria were recorded from three marine sponges where γ-Proteobacteria was dominant class. One potential bacterial strain Halomonas sp. EA423 was selected for identification of bioactive metabolites using GC and LC-MS analyses. Bioactive compounds Sulfamerazine, Metronidazole-OH and Ibuprofen are detected from culture extract of strain Halomonas sp. EA423. Overall, this study gives insight into composition and diversity of antagonistic bacterial community of marine sponges and coral from Red Sea and presence of active metabolites from potential strain. Our results showed that these diverse and potential bacterial communities further need to be studied to exploit their biotechnological significance.

The shield bug, Graphosoma lineatum (Heteroptera, Pentatomidae), harbors extracellular Pantoea‐like symbiont in the enclosed crypts of the midgut. The symbiotic bacteria are essential for normal longevity and fecundity of this insect. In this study, life table analysis was used to assess the biological importance of the gut symbiont in G. lineatum. Considering vertical transmission of the bacterial symbiont through the egg surface contamination, we used surface sterilization of the eggs to remove the symbiont. The symbiont population was decreased in the newborn nymphs hatched from the surface‐sterilized eggs (the aposymbiotic insects), and this reduction imposed strongly negative effects on the insect host. We found significant differences in most life table parameters between the symbiotic insects and the aposymbiotics. The intrinsic rate of increase in the control insects (0.080 ± 0.003 day−1) was higher than the aposymbiotic insects (0.045 ± 0.007 day−1). Also, the net reproductive and gross reproductive rates were decreased in the aposymbiotic insects (i.e., 20.770 ± 8.992 and 65.649 ± 27.654 offspring/individual, respectively), compared with the symbiotic insects (i.e., 115.878 ± 21.624 and 165.692 ± 29.058 offspring/individual, respectively). These results clearly show biological importance of the symbiont in G. lineatum., In this study, life table analysis was used to assess the biological importance of the gut symbiont in the shield bug, Graphosoma lineatum (Heteroptera, Pentatomidae). Surface sterilization of the eggs was used to remove the symbiont. The symbiont population was decreased in the newborn nymphs hatched from the surface‐sterilized eggs (the aposymbiotic insects), and this reduction imposed strongly negative effects on the life history traits of the insect host. We found significant differences in most life table parameters between the symbiotic insects and the aposymbiotics.

The eri silkworm, Samia ricini, is associated with symbiotic bacteria believed to be playing several physiological functions to the host. The larvae of S. ricini were subjected to isolation of gut bacteria using culture-dependent 16S rRNA gene amplification and sequencing; and qualitative and quantitative enzymatic assays. The results of qualitative cellulolytic assays indicated that 58% of the screened gut bacterial isolates had cellulolytic activity. The cellulolytic bacterial isolates belonged to Bacillus sp. (88%), Pseudomonas sp. (8%) and Enterococcus sp. (4%). Quantitative assays indicated that the highest β-glucosidase (13.42 U/mg), endoglucanase (3.60 U/mg) and exoglucanase (2.60 U/mg) activity were in isolates ERI011, ERI009 and ERI097, respectively. Our results further indicate that significant activities of endogenous cellulases are present in the gut fluids of S. ricini. However, a comparative analysis of the cellulolytic activity showed that the endoglucanase activity of bacterial origin was 13 and 18-fold higher in the foregut and midgut, respectively, than that in gut fluids. Similarly, the β-glucosidase activity was 20 and ninefold higher compared with gut fluids from the same compartments. The higher cellulolytic activity of bacterial origin compared with that of insect origin suggests that more cellulose digestion may be aided by cellulases of bacterial origin. These cellulolytic gut bacterial isolates may be good sources for profiling novel genes and biomolecules for biotechnological application.

Wolbachia is a genus of intracellular symbiotic bacteria that are widely distributed in arthropods and nematodes. These maternally inherited bacteria regulate host reproductive systems in various ways to facilitate their vertical transmission. Since the identification of Wolbachia in many insects, the relationship between Wolbachia and the host has attracted great interest. Numerous studies have indicated that Wolbachia modifies a variety of biological processes in the host. Previous studies in Drosophila melanogaster (D. melanogaster) have demonstrated that Wolbachia can affect spermatid differentiation, chromosome deposition, and sperm activity in the early stages of spermatogenesis, leading to sperm dysfunction. Here, we explored the putative effect of Wolbachia in sperm maturation using transcriptomic approaches to compare gene expression in Wolbachia-infected and Wolbachia-free D. melanogaster adult testes. Our findings show that Wolbachia affects many biological processes in D. melanogaster adult testes, and most of the differentially expressed genes involved in carbohydrate metabolism, lysosomal degradation, proteolysis, lipid metabolism, and immune response were upregulated in the presence of Wolbachia. In contrast, some genes that are putatively associated with cutin and wax biosynthesis and peroxisome pathways were downregulated. We did not find any differentially expressed genes that are predicted to be related to spermatogenesis in the datasets. This work provides additional information for understanding the Wolbachia-host intracellular relationships.

Application of plant hormones is an effective strategy to further improve the accumulation of microalgae biomass. In this study, the IAA (indole-3-acetic acid) production capacity of symbiotic bacteria isolated from the culture system of Ochromonas and Chlorella was detected and compared, with the bacterial community structure revealed. The results demonstrated that Algoriphagus, Porphyrobacter, Roseococcus, and Rhizobium were the dominant bacterial genera both in Ochromonas and Chlorella system, distributed in Proteobacteria and Bacteroidetes. Sixteen of 40 strains classified into 15 genera isolated from the two genera of microalgae could produce IAA, with Agrobacterium and Rhizobium as the main representatives with highest IAA production level (22.53–34.18 mg/L in 30 h). And through determination of changes of chlorophyll content in the co-culture system of microalgae and the supernatant of IAA high-yielding bacteria suspension from medium with or without tryptophan (synthetic precursor of IAA), Rhizobium (C-3) and Agrobacterium (O-16, C-2) were proved to promote the growth of Ochromonas and Chlorella through secreting IAA. The biomass yield of Ochromonas and Chlorella could be respectively increased by 78.98% and 72.73% through the co-culture with Agrobacterium (C-2), by 68.15% and 69.93% for Rhizobium (C-3) and by 80.89% and 65.73% for Agrobacterium (O-16). Moreover, compared with the application of exogenous IAA to improve the microalgae biomass, it is more efficient and economical to construct algae bacteria symbiosis system using IAA secretory bacteria commonly existed in microalgae culture system. In addition, the growth promoting effect of IAA secretory bacteria on microalgae was different among the species of algae.

Marine bacteria which are symbionts with Eucheuma sp. and Sargassum sp. has the ability to convert seloluse into glucose. These processes are important during bioethanol production. Identification using PCR and 16S rRNA primers showed that the symbiotic bacteria in Eucheuma sp. was B. subtilis (97% identical to accession number NR. 027552.1) and symbiotic bacteria in Sargassum sp. was B. thuringiensis (97% identical to access number NR. 043403.1). Cellulotic indexes were identified for B. subtilis (2.477 mm) and B. thuringiensis (6.102 mm). Amplification of the endoglucanase gene were conducted with Bac-EuF and Bac-EuR primers in B. subtilis with size at 1416 bp (95% identical to accession number WP_017696508.1), whereas in B. thuriengeinsis the size was 1251 bp (92% identical to the accession number EEM47662). In silico analysis of the endoglucanase gene, showed that the catalytic and cellulose binding domains of B. subtilis were GH5 (aa residue 1-70) and CBM3 (aa residue 131-212), while in B. thuringiensis only GH8 catalytic domains were identified (aa residue 30 -370). The protein motif of the endoglucanase gene B. subtilis and B. thuringiensis had a high similarity characterized by the asn_glycosylation, camp_phospho_site, ck2_phospho_site, myristyl and pkc_phospho_site motif.

The natural nitrogen-15 abundance method does not always make it possible to calculate the rate of symbiotic nitrogen fixation by legumes and needs to be improved. Five legume species typical for the alpine belt of the Teberda Nature Reserve (Anthyllis vulneraria, Astragalus levieri, Hedysarum caucasicum, Oxytropis kubanensis, and Trifolium polyphyllum) have been grown from seeds under conditions of laboratory vegetation experiment. The results show that nodules on the roots of these plants are formed at early stages of their development; Trifolium polyphyllum does not form nodules either under high-mountain conditions or during growth in the laboratory. The natural 15N abundance in the leaves of legume plants in alpine ecosystems makes it possible to calculate the contribution of atmospheric N2 to nitrogen nutrition as early as the first year of their development, while the isotopic nitrogen composition of the roots does not allow this parameter to be determined. The calculation of atmospheric nitrogen fixation rate should take into account isotope fractionation between symbiotic bacteria (nodules) and the host plant; otherwise, the proportion of fixed nitrogen in plant nutrition may be underestimated.

Kappahycus alvarezii is a red alga contained large amount of bioactive material, such as carrageenan. Carrageenan is useful as a raw material for several industries and can be degraded by marine bacteria through breaking the linkages in polysaccharide carrageenan into oligosaccharide carrageenan. The aim of this study is identification of degrading carrageenan in K. alvarezii symbiotic bacteria. The results showed there was 14 isolate bacteria, and all of the isolates have clear zone on congo red staining activity. The isolate bacteria were 7 genera as K. alvarezii symbiotic bacteria, such as Labrenzia sp., Alteromonas sp., Vibrio sp., Celeribacter sp., Pseudoalteromonas sp., Phaeobacter sp. and Cobetia sp. Labrenzia sp., Alteromonas sp., Vibrio sp., Pseudoalteromonas sp., Phaeobacter sp. were recognized to have strong interactions with carrageenan in red algae, while the other Celeribacter sp. and Cobetia sp. have strong interactions with alginate in brown algae.

Background Entomopathogenic nematodes (EPNs) harboring symbiotic bacteria are one of the safest alternatives to the chemical insecticides for the control of various insect pests. Infective juveniles of EPNs locate a target insect, enter through the openings, and reach the hemocoel, where they release the symbiotic bacteria and the target gets killed by the virulence factors of the bacteria. Photorhabdus with Heterorhabditis spp. are well documented; little is known about the associated bacteria. Main body In this study, we explored the presence of symbiotic and associated bacteria from Heterorhabditis sp. (IISR-EPN 09) and characterized by phenotypic, biochemical, and molecular approaches. Six bacterial isolates, belonging to four different genera, were recovered and identified as follows: Photorhabdus luminescens, one each strain of Providencia vermicola, Pseudomonas entomophila, Alcaligenes aquatilis, and two strains of Alcaligenes faecalis based on the phenotypic, biochemical criteria and the sequencing of 16S rRNA gene. Conclusion P. luminescens is symbiotically associated with Heterorhabditis sp. (IISR-EPN 09), whereas P. vermicola, P. entomophila, A. aquatilis, and A. faecalis are the associated bacteria. Further studies are needed to determine the exact role of the bacterial associates with the Heterorhabditis sp.

Rapid spread of vector borne diseases, especially through mosquitoes is in alarming rise worldwide. Among mosquitoes, Aedes aegypti is a major vector transmitting arboviruses such as dengue and zika to human population. The ineffectiveness of control measures against these arboviruses has necessitated alternate strategies to curb disease transmission. Recent studies show that symbiotic bacteria from insects hinder pathogen transmission by altering vector competence. Therefore, analyzing the bacterial communities of mosquitoes is essential to identify potential bacteria that play a critical role in vector competence. Salivary gland, a key organ in viral transmission however, is minimally explored towards their microbiota. In this study, we have screened 28 bacterial isolates from salivary glands of non-blood fed (NBF) and blood fed (BF) female Ae. aegypti, collected from the field population of Coimbatore, India. Among them, 11 bacterial species from distinct genera belonging to three major phyla; Proteobacteria, Firmicutes and Actinobacteria were identified through 16S rRNA gene sequencing. Interestingly, the differences in bacterial species associated with salivary glands were clearly discernible. This suggests that the dynamics of bacterial population after blood feeding is not restricted to the mosquito gut, but envisioned in the salivary glands as well. Overall, the results shed more light into the understating on salivary glands microbiota of dreadful vector Ae. aegypti.

Summary Holobiont phenotype results from a combination of host and symbiont genotypes as well as from prevailing environmental conditions that alter the relationships among symbiotic members. Corals exemplify this concept, where shifts in the algal symbiont community can lead to some corals becoming more or less thermally tolerant. Despite linkage between coral bleaching and disease, the roles of symbiotic bacteria in holobiont resistance and susceptibility to disease remains less well understood. This study thus characterizes the microbiome of disease‐resistant and ‐susceptible Acropora cervicornis coral genotypes (hereafter referred to simply as ‘genotypes’) before and after high temperature‐mediated bleaching. We found that the intracellular bacterial parasite ‘Ca. Aquarickettsia rohweri’ was strikingly abundant in disease‐susceptible genotypes. Disease‐resistant genotypes, however, had notably more diverse and even communities, with correspondingly low abundances of ‘Ca. Aquarickettsia’. Bleaching caused a dramatic reduction of ‘Ca. Aquarickettsia’ within disease‐susceptible corals and led to an increase in bacterial community dispersion, as well as the proliferation of opportunists. Our data support the hypothesis that ‘Ca. Aquarickettsia’ species increase coral disease risk through two mechanisms: (i) the creation of host nutritional deficiencies leading to a compromised host‐symbiont state and (ii) the opening of niche space for potential pathogens during thermal stress.

Infectious diseases are one of the major drivers of coral reef decline worldwide. White plague-like disease (WPL) is a widespread disease with a complex etiology that infects several coral species, including the Brazilian endemic species Mussismilia braziliensis. Gene expression profiles of healthy and WPL-affected M. braziliensis were analyzed in winter and summer seasons. The de novo assembly of the M. braziliensis transcriptome from healthy and white plague samples produced a reference transcriptome containing 119,088 transcripts. WPL-diseased samples were characterized by repression of immune system and cellular defense processes. Autophagy and cellular adhesion transcripts were also repressed in WPL samples, suggesting exhaustion of the coral host defenses. Seasonal variation leads to plasticity in transcription with upregulation of intracellular signal transduction, apoptosis regulation, and oocyte development in the summer. Analysis of the active bacterial rRNA indicated that Pantoea bacteria were more abundant in WPL corals, while Tistlia, Fulvivirga, and Gammaproteobacteria Ga0077536 were more abundant in healthy samples. Cyanobacteria proliferation was also observed in WPL, mostly in the winter. These results indicate a scenario of dysbiosis in WPL-affected M. braziliensis, with the loss of potentially symbiotic bacteria and proliferation of opportunistic microbes after the start of the infection process.

Aphids are a diverse family of crop pests. Aphids formed a complex relationship with intracellular bacteria. Depending on the region of study, the species composition of both aphids and their facultative endosymbionts varies. The aim of the work was to determine the occurrence and genetic diversity of Wolbachia, Spiroplasma and Rickettsia symbionts in aphids collected in 2018-2019 in Moscow. For these purposes, 578 aphids from 32 collection sites were tested by PCR using specific primers. At least 21 species of aphids from 14 genera and four families were identified by barcoding method, of which 11 species were infected with endosymbionts. Rickettsia was found in six species, Wolbachia in two species, Spiroplasma in one species. The presence of Rickettsia in Impatientinum asiaticum, Myzus cerasi, Hyalopterus pruni, Eucallipterus tiliae, Chaitophorus tremulae and Wolbachia in Aphis pomi and C. tremulae has been described for the first time. A double infection with Rickettsia and Spiroplasma was detected in a half of pea aphid (Acyrthosiphon pisum) individuals. For the first time was found that six species of aphids are infected with Rickettsia that are genetically different from previously known. It was first discovered that A. pomi is infected with two Wolbachia strains, one of which belongs to supergroup B and is genetically close to Wolbachia from C. tremulae. The second Wolbachia strain from A. pomi belongs to the supergroup M, recently described in aphid species. Spiroplasma, which we observed in A. pisum, is genetically close to male killing Spiroplasma from aphids, ladybirds and moths. Both maternal inheritance and horizontal transmission are the pathways for the distribution of facultative endosymbiotic bacteria in aphids.Тли – разнообразное семейство вредителей сельскохозяйственных культур. Тли сформировали сложную взаимосвязь с внутриклеточными бактериями, известными как эндосимбионты, которые оказывают как положительное, так и отрицательное влияние на хозяина, что может иметь практическое значение. В раз- ных регионах мира состав факультативных симбионтов в популяциях тлей варьирует. Задачей работы было установить распространение и генетическое разнообразие симбионтов Wolbachia, Spiroplasma и Rickettsia в тлях, собранных в 2018–2019 гг. в Москве и Подмосковье. Для этого 578 тлей из 32 мест сбора тестировали методом ПЦР, используя специфические праймеры для мтДНК тлей, Wolbachia, Spiroplasma и Rickettsia. Мето- дом молекулярно-генетического анализа определено не менее 21 вида тлей из 14 родов и четырех семейств. Одиннадцать видов оказались инфицированы эндосимбионтами, а именно: у шести видов обнаружены Rickettsia, у двух видов – Wolbachia, у одного – Spiroplasma. Впервые выявлено заражение бактерией Rickettsia у Impatientinum asiaticum, Myzus cerasi, Hyalopterus pruni, Eucallipterus tiliae, Chaitophorus tremulae и бактерией Wolbachia у Aphis pomi и C. tremulae. У половины особей гороховой тли Acyrthosiphon pisum установлено двой- ное заражение Rickettsia и Spiroplasma. Впервые выявлены риккетсии у шести видов тлей, которые генетиче- ски отличаются от известных ранее. Впервые обнаружено заражение яблонной тли A. pomi двумя штаммами Wolbachia, причем один из штаммов относится к супергруппе В и генетически близок с Wolbachia из осино- вой тли C. tremulae, а второй штамм относится к супергруппе М, недавно описанной у видов тлей. Spiroplasma, найденная нами у A. pisum, генетически близка Spiroplasma, вызывающей андроцид у тлей, божьих коровок и молей, и кластеризуется с S. ixodetis. Разнообразие ДНК симбионтов убедительно свидетельствует о том, что как материнское наследование, так и горизонтальный перенос являются путями распространения факульта- тивных бактерий у тлей.

The dialog between microbes and immune cells is critical for the establishment and maintenance of immune homeostasis. Bacterial-derived metabolites or structural components initiate immune signaling pathways and transcriptional factors, inducing a broad range of specificities and functional repertoires of the immune cells. Conversely, the immune system regulates the composition and function of bacterial communities. Elements of the adaptive immunity, including maternal antibodies and mucosal antibody responses, play crucial roles in protecting the hosts from pathogens in addition to promoting colonization of symbiotic bacteria at mucosal surfaces. The complex interactions set from an early stage in life between the microbiota and adaptive immunity, impact other major physiological systems. In this review, we summarize recent advances in our understanding of how gut bacteria regulate systemic homeostasis by highlighting the finely orchestrated interactions between gut bacteria, immune responses and the nervous system.

Metazoans harbor a wealth of symbionts that are ever-changing the environment by taking up resources and/or excreting metabolites. One such common environmental modification is a change in pH. Conventional wisdom holds that symbionts facilitate the survival and production of their hosts in the wild, but this notion lacks empirical evidence. Here, we report that symbiotic bacteria in the genus Enterococcus attenuate the oviposition avoidance of alkaline environments in Drosophila. We studied the effects of alkalinity on oviposition preference for the first time, and found that flies are robustly disinclined to oviposit on alkali-containing substrates. This innate repulsion to alkaline environments is explained, in part, by the fact that alkalinity compromises the health and lifespan of both offspring and parent Drosophila. Enterococcus dramatically diminished or even completely reversed the ovipositional avoidance of alkalinity in Drosophila. Mechanistically, Enterococcus generate abundant lactate during fermentation, which neutralizes the residual alkali in an egg-laying substrate. In conclusion, Enterococcus protects Drosophila from alkali stress by acidifying the ovipositional substrate, and ultimately improves the fitness of the Drosophila population. Our results demonstrate that symbionts are profound factors in the Drosophila ovipositional decision, and extend our understanding of the intimate interactions between Drosophila and their symbionts.

The bacterial gut microbiota of many animals is known to be important for many physiological functions including detoxification. The selective pressures imposed on insects by exposure to toxins may also be selective pressures on their symbiotic bacteria, who thus may contribute to the mechanism of toxin tolerance for the insect. Amatoxins are a class of cyclopeptide mushroom toxins that primarily act by binding to RNA polymerase II and inhibiting transcription. Several species of mycophagous Drosophila are tolerant to amatoxins found in mushrooms of the genus Amanita, despite these toxins being lethal to most other known eukaryotes. These species can tolerate amatoxins in natural concentrations to utilize toxic mushrooms as larval hosts, but the mechanism by which these species are tolerant remains unknown. Previous data have shown that a local population of D. tripunctata exhibits significant genetic variation in toxin tolerance. This study assesses the potential role of the microbiome in α‐amanitin tolerance in six wild‐derived strains of Drosophila tripunctata. Normal and antibiotic‐treated samples of six strains were reared on diets with and without α‐amanitin, and then scored for survival from the larval stage to adulthood and for development time to pupation. Our results show that a substantial reduction in bacterial load does not influence toxin tolerance in this system, while confirming genotype and toxin‐specific effects on survival are independent of the microbiome composition. Thus, we conclude that this adaptation to exploit toxic mushrooms as a host is likely intrinsic to the fly's genome and not a property of their microbiome.

Parasites and bacteria have co-evolved with humankind, and they interact all the time in a myriad of ways. For example, some bacterial infections result from parasite-dwelling bacteria as in the case of Salmonella infection during schistosomiasis. Other bacteria synergize with parasites in the evolution of human disease as in the case of the interplay between Wolbachia endosymbiont bacteria and filarial nematodes as well as the interaction between Gram-negative bacteria and Schistosoma haematobium in the pathogenesis of urinary bladder cancer. Moreover, secondary bacterial infections may complicate several parasitic diseases such as visceral leishmaniasis and malaria, due to immunosuppression of the host during parasitic infections. Also, bacteria may colonize the parasitic lesions; for example, hydatid cysts and skin lesions of ectoparasites. Remarkably, some parasitic helminths and arthropods exhibit antibacterial activity usually by the release of specific antimicrobial products. Lastly, some parasite–bacteria interactions are induced as when using probiotic bacteria to modulate the outcome of a variety of parasitic infections. In sum, parasite–bacteria interactions involve intricate processes that never cease to intrigue the researchers. However, understanding and exploiting these interactions could have prophylactic and curative potential for infections by both types of pathogens.

Symbiotic microbes play a crucial role in regulating parasite-host interactions; however, the role of bacterial associates in parasite-host interactions requires elucidation. In this study, we showed that, instead of introducing numerous symbiotic bacteria, dispersal of 4th-stage juvenile (JIV ) pinewood nematodes (PWNs), Bursaphelenchus xylophilus, only introduced few bacteria to its vector beetle, Monochamus alternatus (Ma). JIV showed weak binding ability to five dominant bacteria species isolated from the beetles' pupal chamber. This was especially the case for binding to the opportunistic pathogenic species Serratia marcescens; the nematodes' bacteria binding ability at this critical stage when it infiltrates Ma for dispersal was much weaker compared with Caenorhabditis elegans, Diplogasteroides asiaticus, and propagative-stage PWN. The associated bacterium S. marcescens, which was isolated from the beetles' pupal chambers, was unfavorable to Ma, because it caused a higher mortality rate upon injection into tracheae. In addition, S. marcescens in the tracheae caused more immune effector disorders compared with PWN alone. Ma_Galectin2 (MaGal2), a pattern-recognition receptor, was up-regulated following PWN loading. Recombinant MaGal2 protein formed aggregates with five dominant associated bacteria in vitro. Moreover, MaGal2 knockdown beetles had up-regulated prophenoloxidase gene expression, increased phenoloxidase activity, and decreased PWN loading. Our study revealed a previously unknown strategy for immune evasion of this plant pathogen inside its vector, and provides novel insights into the role of bacteria in parasite-host interactions.

Pigmented bacterial symbionts play major roles in the health of coral holobionts. However, there is scarce knowledge on the diversity of these microbes for several coral species. To gain further insights into holobiont health, pigmented bacterial isolates of Fabibacter pacificus (Bacteroidetes; n = 4), Paracoccus marcusii (Alphaproteobacteria; n = 1), and Pseudoalteromonas shioyasakiensis (Gammaproteobacteria; n = 1) were obtained from the corals Mussismilia braziliensis and Montastraea cavernosa in Abrolhos Bank, Brazil. Cultures of these bacterial symbionts produced strong antioxidant activity (catalase, peroxidase, and oxidase). To explore these bacterial isolates further, we identified their major pigments by HPLC and mass spectrometry. The six phylogenetically diverse symbionts had similar pigment patterns and produced myxol and keto-carotene. In addition, similar carotenoid gene clusters were confirmed in the whole genome sequences of these symbionts, which reinforce their antioxidant potential. This study highlights the possible roles of bacterial symbionts in Montastraea and Mussismilia holobionts.

For sustainable agriculture in saline soil, extensive exploitation of salt-tolerant plant growth-promoting (PGP) bacteria and other symbiotic bacteria is required. This study was carried out to evaluate the efficiency of native salt-tolerant rice rhizobacteria for plant growth promotion under salt stress. A total of 188 bacteria were screened for assessing salt-tolerant capacity and nine isolates tolerating 12% NaCl (w/v) concentration were selected. Biochemical and molecular identification revealed that the salt-tolerant bacteria belonged to Bacillus sp, Exiguobacterium sp, Enterobacter sp, Lysinibacillus sp, Stenotrophomonas sp, Microbacterium sp, and Achromobacter sp. The increase in NaCl concentration from 2 to 4% decreases the PGP activities such as IAA production, P solubilization, K solubilization, and nitrate reduction. The effects of inoculation of salt-tolerant bacteria on the growth and different physiological properties of rice (Oryza sativa) were studied. It was found that the salinity affected the root and shoot length of the control plants; however, bacterial inoculant were found to effectively promote the growth of paddy under salinity stress. Further, bacterial inoculants substantially enhanced total chlorophyll, proline, total phenol, and oxidative damage such as electrolyte leakage and membrane stability index under salt stress. This study suggests that salt-tolerant PGP bacteria may be used for cultivation of O. sativa in salinized agricultural lands.

Many invertebrates develop into different color morphs in response to changes in environmental conditions. Color morphs can differ in their biology and stress tolerance including pesticide resistance, but underlying mechanisms are unclear. In this study, we found that yellow morphs (predominant in hot summer conditions) of an agricultural pest, the melon aphid Aphis gossypii, have higher levels of resistance to the commonly used pesticides imidacloprid and sulfoxaflor compared to the green morphs (predominant in cooler spring and autumn conditions), while no difference was found in morph resistance to the antibiotic/pesticide avermectin. Transcriptome analysis and biochemical assays of enzyme activities revealed no differences in metabolic processes between the two color morphs except for differentially expressed genes related to wing development. Microbiome analysis revealed that the endosymbiont Buchnera aphidicola is the dominant bacterium in both morphs, representing 86.76–99.88% of the microbiome. The yellow morph had a higher density of Buchnera compared to the green morph. When yellow morphs were treated with avermectin and antibiotics, the density of Buchnera was reduced to levels similar to the green morph, and their susceptibility to imidacloprid was simultaneously increased. These results indicate an association between resistance in the yellow morph of A. gossypii and symbiotic bacteria, providing novel insights into pesticide resistance mechanisms and the plasticity of stress adaptation.