Search

Abstract Studies on Bdellovibrio and like organisms (BALOs), obligate predatory bacteria, have highlighted the possibility of regulating bacteria and biofilms; however, yak-derived BALOs are yet to be reported. We aimed to characterize the BALOs isolated and identified from yak (Bos grunniens) feces and examine application potential. BALOs were isolated from healthy yak fecal samples, with Escherichia coli (ATCC 25922) as prey using the double-layer agar method, identified by transmission electron microscopy (TEM), and the specific 16S rDNA sequencing analysis. Sequencing of the 16S rDNA gene indicated that this isolate was 91% similar to the Bdellovibrio sp. NC01 reference strain and was named YBD-1. Proportion of YBD-1 lysed bacteria is 12/13. The YBD-1 showed best growth at 25–40°C, 0–0.25% (w/v) NaCl, and pH 6.5–7.5. YBD-1 significantly reduced the planktonic cells and biofilms of E.coli in co-culture compared to the E.coli group. Additionally, SEM analysis indicated that YBD-1 significantly reduced biofilm formation in E. coli. Furthermore, quantitative Real Time-polymerase chain reaction (qRT-PCR) showed that the expression of the virulence genes fim and iroN and the genes pgaABC involved in biofilm formation went down significantly. We concluded that YBD-1 may have the potential to control bacterial growth and biofilm-associated bacterial illnesses.

Biofilms are a major concern within the food industry since they have the potential to reduce productivity in situ (within the field), impact food stability and storage, and cause downstream food poisoning. Within this review, predatory bacteria as potential biofilm control and eradication agents are discussed, with a particular emphasis on the intraperiplasmic Bdellovibrio-and-like organism (BALO) grouping. After providing a brief overview of predatory bacteria and their activities, focus is given to how BALOs fulfill four attributes that are essential for biocontrol agents to be successful in the food industry: (1) Broad spectrum activity against pathogens, both plant and human; (2) Activity against biofilms; (3) Safety towards humans and animals; and (4) Compatibility with food. As predatory bacteria possess all of these characteristics, they represent a novel form of biofilm biocontrol that is ripe for use within the food industry. [ABSTRACT FROM AUTHOR]

Predation structures food webs, influences energy flow, and alters rates and pathways of nutrient cycling through ecosystems, effects that are well documented for macroscopic predators. In the microbial world, predatory bacteria are common, yet little is known about their rates of growth and roles in energy flows through microbial food webs, in part because these are difficult to quantify. Here, we show that growth and carbon uptake were higher in predatory bacteria compared to nonpredatory bacteria, a finding across 15 sites, synthesizing 82 experiments and over 100,000 taxon-specific measurements of element flow into newly synthesized bacterial DNA. Obligate predatory bacteria grew 36% faster and assimilated carbon at rates 211% higher than nonpredatory bacteria. These differences were less pronounced for facultative predators (6% higher growth rates, 17% higher carbon assimilation rates), though high growth and carbon assimilation rates were observed for some facultative predators, such as members of the genera Lysobacter and Cytophaga, both capable of gliding motility and wolf-pack hunting behavior. Added carbon substrates disproportionately stimulated growth of obligate predators, with responses 63% higher than those of nonpredators for the Bdellovibrionales and 81% higher for the Vampirovibrionales, whereas responses of facultative predators to substrate addition were no different from those of nonpredators. This finding supports the ecological theory that higher productivity increases predator control of lower trophic levels. These findings also indicate that the functional significance of bacterial predators increases with energy flow and that predatory bacteria influence element flow through microbial food webs.IMPORTANCE The word "predator" may conjure images of leopards killing and eating impala on the African savannah or of great white sharks attacking elephant seals off the coast of California. But microorganisms are also predators, including bacteria that kill and eat other bacteria. While predatory bacteria have been found in many environments, it has been challenging to document their importance in nature. This study quantified the growth of predatory and nonpredatory bacteria in soils (and one stream) by tracking isotopically labeled substrates into newly synthesized DNA. Predatory bacteria were more active than nonpredators, and obligate predators, such as Bdellovibrionales and Vampirovibrionales, increased in growth rate in response to added substrates at the base of the food chain, strong evidence of trophic control. This work provides quantitative measures of predator activity and suggests that predatory bacteria-along with protists, nematodes, and phages-are active and important in microbial food webs.

The present study investigated the predatory efficacy of Bdellovibrio isolated from untreated hospital wastewater sources against human pathogens. Bdellovibrio is a Gram-negative, motile, uniflagellate predatory bacteria present in the environment, which directly predates on other bacteria, including human pathogens. In the present study, 30 hospital effluent samples were collected and screened for Bdellovibrio. A total of 11 Bdellovibrio isolates were obtained by the double-layer agar technique. All the isolates were identified by amplification of the 16S rDNA coding region using polymerase chain reaction (PCR) and confirmed as Bdellovibrio stolpii. The lytic activity of confirmed isolates was investigated against four Gram-negative bacteria Pseudomonas aeruginosa ADW44, Pseudomonas aeruginosa 27853(ATCC Strain), V. cholerae and Salmonella typhimurium of clinical origin obtained from the institutional repository. Among the 11 isolates, three Bdellovibrio isolates NBd1, YBd1 and RBd1 demonstrated the ability to prey upon the tested clinical isolates. To the best of our knowledge, this is the first report on the isolation of B. stolpii from hospital wastewater settings in India with broad and high bacteriolytic activity. HIGHLIGHT Antibiotic resistance in bacteria is a major concern in both national and international scenarios.; The study gives insights into the predatory spectrum of Bdellovibrio, against multidrug-resistant bacteria.; The present study may help in the development of Bdellovibrio as a whole-organism approach against biofilm-forming bacteria.; Developing more efficient, economic, and environmentally friendly biocontrol agents against multidrug-resistant bacteria is the need of the hour.;

Aim: The aim of this study was to evaluate the effects of Bdellovibrio bacteriovorus HD100 on experimental periodontitis (EP) in rats. Methods: Thirty‐two rats were divided into four groups: control, C‐HD100 (B. bacteriovorus), EP, and EP‐HD100. On day 0, EP was induced by the placement of cotton ligatures around the mandibular first molars (MFMs) in the EP and EP‐HD100 groups. In the C‐HD100 and EP‐HD100 groups, suspensions containing 1 × 109 PUF/ml of B. bacteriovorus HD100 were topically administered to the subgingival region of MFMs on days 0, 3, and 7. Animals were euthanized on day 14. Morphometrics analyses were performed in hemimandibles. The levels of tumor necrosis factor alpha (TNF‐α), interleukin (IL)‐6, monocyte chemoattractant protein (MCP)‐1, IL‐10, IL‐1β, transforming growth factor beta (TGF‐β), macrophage colony‐stimulating factor (M‐CSF) and regulated on activation and normal T cell expressed and secreted (RANTES) were determined by enzymatic immunoassays in gingival tissues. Beta defensin (BD)‐1, BD‐2, and BD‐3, Toll‐like receptors (TLR)‐2 and TLR‐4, and a cluster of differentiation (CD)‐4, CD‐8 and CD‐57 were analyzed by immunohistochemistry in hemimandibles. Data were statistically analyzed. Results: The EP group showed greater alveolar bone loss than EP‐HD100 (p <.05). The EP‐HD100 group showed higher levels of MCP‐1, RANTES, IL‐10, and TGF‐β, lower levels of TNF‐α than the EP group (p <.05). No differences were observed in IL‐1β, IL‐6, and M‐CSF levels between EP and EP‐HD100 groups. The C‐HD100 group had higher IL‐6, TNF‐α, RANTES, and MCP‐1 levels than the control group (p <.05). Regarding BD, the EP‐HD100 group showed a larger immunolabeling pattern for BD‐1, BD‐2, and BD‐3 than the EP group (p <.05). No significant differences in the immunolabeling pattern were observed for TLR‐2, TLR‐4, CD‐4, CD‐8, and CD‐57 between EP and EP‐HD100 groups. Conclusion: The topical use of B. bacteriovorus HD100 reduces alveolar bone loss, increases expression of BD, and modulates the cytokines levels on periodontal tissues in rats with EP. [ABSTRACT FROM AUTHOR]

The present study investigated the predatory efficacy of Bdellovibrio isolated from untreated hospital wastewater sources against human pathogens. Bdellovibrio is a Gram-negative, motile, uniflagellate predatory bacteria present in the environment, which directly predates on other bacteria, including human pathogens. In the present study, 30 hospital effluent samples were collected and screened for Bdellovibrio. A total of 11 Bdellovibrio isolates were obtained by the double-layer agar technique. All the isolates were identified by amplification of the 16S rDNA coding region using polymerase chain reaction (PCR) and confirmed as Bdellovibrio stolpii. The lytic activity of confirmed isolates was investigated against four Gram-negative bacteria Pseudomonas aeruginosa ADW44, Pseudomonas aeruginosa 27853(ATCC Strain), V. cholerae and Salmonella typhimurium of clinical origin obtained from the institutional repository. Among the 11 isolates, three Bdellovibrio isolates NBd1, YBd1 and RBd1 demonstrated the ability to prey upon the tested clinical isolates. To the best of our knowledge, this is the first report on the isolation of B. stolpii from hospital wastewater settings in India with broad and high bacteriolytic activity [ABSTRACT FROM AUTHOR]

The Pectobacterium and Dickeya pectinolytic bacteria are phytopathogens responsible for several macerating diseases on a wide range of crops and ornamental plants. Recently, bacterial predators belonging to the Bdellovibrio and like organisms (BALOs) were shown to efficiently prey on these rot-causing bacteria and reduce soft rot-induced potato slice maceration. In the current research, our novel approach aimed at developing and studying a κ-carrageenan-based encapsulation system for fast-release of entrapped B. bacteriovorus HD100 in high numbers to prevent bacterial soft-rot infections. κ-carrageenan-dried carriers swelled and dissolved upon immersion in water due to a loss of potassium ions which are the main cross-linking agents. Survival rates of the predators after drying were higher for immobilized bdelloplasts (e.g., predator inside the host) compared to attack phase (host-searching, AP) cells, and with the addition of the osmoprotectant trehalose to the carriers. Released encapsulated predators preyed efficiently on soft rot bacteria, with bdelloplasts performing better as compared to AP cells. However, predation dynamics were influenced by the type of added osmoprotectant. Carrageenan-trehalose carriers encapsulating predators were able to reduce soft-rot disease in situ using a potato slice assay. To our knowledge, this research is the first to explore the potential of encapsulated BALOs against phytopathogens. Key points: • Dissolution of the carriers was affected by potassium concentration in the system. • Encapsulation of bdelloplasts with trehalose best maintained the predator viability. • The encapsulated predators efficiently controlled soft rot in vitro and in situ. [ABSTRACT FROM AUTHOR]

ABSTRACT While diverse antibacterials are available in nature, each possesses their own strengths and limitations. One such antibacterial is colicins, proteinaceous toxins that are produced by strains of E. coli to subvert the growth or viability of other E. coli strains. Similarly, predatory bacteria, of which Bdellovibrio bacteriovorus is well-known, are microbes that actively predate on and consume other Gram-negative bacterial strains. While they are all quite active as antibacterials, they also present some limitations: rapid resistance development to colicins while predation does not completely kill their prey. Within this study, therefore, we evaluated the impact of two different colicins (colicin B [ColB] and colicin E5 [ColE5]) and B. bacteriovorus HD100 either individually or together against four clinical isolates of E. coli that are resistant to either colistin or carbapenem. While the ColB and ColE5 were quickly active when used alone, causing a significant loss in viability (>3-log) in susceptible populations after only 3 h, the pathogens always grew afterwards and had final cell densities that were similar with their respective controls. Predation with B. bacteriovorus HD100, in contrast, was most pronounced after 24 h (>3-log reduction in each pathogen viability but never complete). When combined, better killing efficiencies were observed with several of the pathogens, with complete eradication realized for two (

The ImpX transporters of the drug/metabolite transporter superfamily were first proposed to transport riboflavin (RF; vitamin B2) based on findings of a cis-regulatory RNA element responding to flavin mononucleotide (an FMN riboswitch). Bdellovibrio exovorous JSS has a homolog belonging to this superfamily. It has 10 TMSs and shows 30% identity to the previously characterized ImpX transporter from Fusobacterium nucleatum. However, the ImpX homolog is not regulated by an FMN-riboswitch. In order to test the putative function of the ImpX homolog from B. exovorous (BexImpX), we cloned and heterologously expressed its gene. We used functional complementation, growth inhibition experiments, direct uptake experiments and inhibition studies, suggesting a high degree of specificity for RF uptake. The EC50 for growth with RF was estimated to be in the range 0.5-1 µM, estimated from the half-maximal RF concentration supporting the growth of a RF auxotrophic Escherichia coli strain, but the Khalf for RF uptake was 20 µM. Transport experiments suggested that the energy source is the proton motive force but that NaCl stimulates uptake. Thus, members of the ImpX family members are capable of RF uptake, not only in RF prototrophic species such as F.  nucleatum, but also in the B2 auxotrophic species, B. exovorous.

Bdellivibrio could be recognized for its efficacy as a "living antibiotic" against Gram-negative bacteria and holds potential applications in aquaculture. Nevertheless, the safety implications of prolonged Bdellivibrio administration in aquaculture remain unexplored. This study aimed to investigate the impact of continuous Bdellovibrio supplementation to zebrafish culturing water over a 6-month period, spanning from larvae to adult fish. Assessments encompassed the influence on growth indicators, intestinal flora distribution, and resistance to pathogenic bacterial infections. Contrary to expectations, Bdellovibrio exhibited minimal effects on the growth parameters (body length and weight) of zebrafish, however, a notable increase in survival rates was observed. 16S rRNA sequencing revealed a significant enhancement in the diversity and abundance of intestinal microorganisms in zebrafish. Notably, the abundance of Planctomycetes increased, while potential pathogenic bacteria such as Aeromonas, Pirellula, and Flavobacterium decreased in the zebrafish intestine. Under Edwardsiella anguillarum immersion infections, Bdellovibrio significantly boosted the survival rate of zebrafish, concomitant with a continuous rise in Bdellovibrio levels in the breeding water. This comprehensive analysis sheds light on the safety of prolonged Bdellovibrio use and its protective efficacy against pathogenic bacterial infections. The findings not only elucidate the mechanisms through which Bdellovibrio safeguards fish from bacterial infections but also furnish essential theoretical foundations for the secure integration of Bdellovibrio in aquaculture. • Long-term use of Bdellovibrio has not adversely effects on the growth of zebrafish. • Bdellovibrio could significantly increase the diversity and abundance of zebrafish intestinal microorganisms. • The Bdellovibrio could increase the abundance of Planctomycetes, and decrease the potential pathogenic bacteria in zebrafish intestine. • Bdellovibrio could significantly increase the survival rate of zebrafish under E. anguillarum immersion infections. [ABSTRACT FROM AUTHOR]

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by sacroiliac joint lesions and spinal ascending involvement. The aim of this work was at investigating the gut microbiota profile and proinflammatory cytokines in AS patients. Gut microbiota of AS patients was clearly different from that of healthy human controls. 16S rRNA sequencing analysis demonstrated a changed microbial diversity in the AS patients, and there was a significant increase in the abundance of Cyanobacteria, Deinococcota, Patescibacteria, Actinobacteriota, and Synergistota at a phyla level increased in AS, while the relative abundance of Acidobacteriota, Bdellovibrionota, Campylobacterota, Chloroflexi, Gemmatimonadota, Myxococcota, Nitrospirota, Proteobacteria, and Verrucomicrobiota declined in AS patients. ELISA results for the markers of inflammation in the AS patients revealed increased concentrations of proinflammatory cytokines such as IL-23, IL-17, and IFN-γ. Our findings support the fact that the intestinal microbiota are altered in AS with an inflammatory status, which indicates that gut microbiota should be a potential target for ankylosing spondylitis therapy. [ABSTRACT FROM AUTHOR]

Bdellovibrio, δ-proteobacteria, including B. bacteriovorus (Bba) and B. exovorus (Bex), are obligate predators of other Gram-negative bacteria. While Bba grows in the periplasm of the prey cell, Bex grows externally. We have analyzed and compared the transport proteins of these 2 organisms based on the current contents of the Transporter Classification Database (TCDB; www.tcdb.org). Bba has 103 transporters more than Bex, 50% more secondary carriers, and 3 times as many MFS carriers. Bba has far more metabolite transporters than Bex as expected from its larger genome, but there are 2 times more carbohydrate uptake and drug efflux systems, and 3 times more lipid transporters. Bba also has polyamine and carboxylate transporters lacking in Bex. Bba has more than twice as many members of the Mot-Exb family of energizers, but both may have energizers for gliding motility. They use entirely different types of systems for iron acquisition. Both contain unexpectedly large numbers of pseudogenes and incomplete systems, suggesting that they are undergoing genome size reduction. Interestingly, all 5 outer-membrane receptors in Bba are lacking in Bex. The 2 organisms have similar numbers and types of peptide and amino acid uptake systems as well as protein and carbohydrate secretion systems. The differences observed correlate with and may account, in part, for the different lifestyles of these 2 bacterial predators.

Bdellovibrio, δ-proteobacteria, including B. bacteriovorus (Bba) and B. exovorus (Bex), are obligate predators of other Gram-negative bacteria. While Bba grows in the periplasm of the prey cell, Bex grows externally. We have analyzed and compared the transport proteins of these 2 organisms based on the current contents of the Transporter Classification Database (TCDB; www.tcdb.org). Bba has 103 transporters more than Bex, 50% more secondary carriers, and 3 times as many MFS carriers. Bba has far more metabolite transporters than Bex as expected from its larger genome, but there are 2 times more carbohydrate uptake and drug efflux systems, and 3 times more lipid transporters. Bba also has polyamine and carboxylate transporters lacking in Bex. Bba has more than twice as many members of the Mot-Exb family of energizers, but both may have energizers for gliding motility. They use entirely different types of systems for iron acquisition. Both contain unexpectedly large numbers of pseudogenes and incomplete systems, suggesting that they are undergoing genome size reduction. Interestingly, all 5 outer-membrane receptors in Bba are lacking in Bex. The 2 organisms have similar numbers and types of peptide and amino acid uptake systems as well as protein and carbohydrate secretion systems. The differences observed correlate with and may account, in part, for the different lifestyles of these 2 bacterial predators.

A countermeasure based on ZnO assistant Bdellovibrio (ZnO@Bdello) was reported to remove biofilm in periodontitis. ZnO@Bdello can remove Gram-negative bacteria biofilm, thereby alleviating inflammation, inhibiting bone resorption, and exhibiting an excellent effect in the treatment of periodontitis. [Display omitted] Periodontitis is caused by subgingival plaque biofilm mainly composed of Gram-negative bacteria, affecting human populations at a high prevalence. Antibiotics therapy is the traditional method for periodontitis, but its efficiency in removing plaque biofilm is limited. With the aim to find an effective therapeutic method to treat periodontitis, we reported a material-assistant micro-organism (MAMO) strategy to eradicate Gram-negative bacteria biofilm using ZnO nanorods engineered Bdellovibrio (ZnO@Bdello). Bdellovibrio bacteriovorus is a natural Gram-negative bacteria predator with strong motility. ZnO nanorods are a kind of common piezoelectric material that senses mechanical pressure and produces reactive oxygen species (ROS). During the predation process of Bdellovibrio , the collision of Bdellovibrio triggered ZnO nanorods to produce ROS to enhance the removal of plaque biofilm. Both in vitro and in vivo studies showed ZnO@Bdello could remove biofilm effectively. In addition, ZnO@Bdello possessed superior competence in alleviating inflammation and inhibiting bone resorption in rats and rabbit periodontitis models. Importantly, this strategy does not induce detectable pathogen resistance and side effects. [ABSTRACT FROM AUTHOR]

ABSTRACT Bdellovibrio bacteriovorus is a predatory, Gram-negative bacteria that feeds on many pathogenic bacteria and has been investigated as a possible solution for mitigating biofilms in different fields. The application depends on more fundamental ecological studies into the dynamics between Bdellovibrio and their prey. To do so requires an accurate, reliable, and, preferably rapid, way of enumerating the cells. Flow cytometry (FCM) is potentially a rapid, accurate, and inexpensive tool for this, but it has yet to be validated in the enumeration of Bdellovibrio. In this study, we developed a protocol to measure the number of Bdellovibrio in samples of various densities using FCM and compared the results with those of other methods: optical density (OD), PFU assay (PFU), and quantitative PCR (qPCR). We observed a strong correlation between values obtained using FCM and PFU (ρ = 0.923) and FCM and qPCR (ρ = 0.987). Compared to optical density there was a much weaker correlation (ρ = 0.784), which was to be expected given the well-documented uncertainty in converting optical density (OD) to cell numbers. The FCM protocol was further validated by demonstrating its ability to distinguish and count mixed populations of Bdellovibrio and the prey Pseudomonas. Thus, the accuracy of FCM as well as its speed and reproducibility make it a suitable alternative for measuring Bdellovibrio cell numbers, especially where many samples are required to capture the dynamics of predator-prey interactions. IMPORTANCE The rise of antibiotic resistance and the unwanted growth of bacteria is a universally growing problem. Predatory bacteria can be used as a biological alternative to antibiotics because they grow by feeding on other bacteria. To apply this effectively requires further study and a deeper understanding of the forces that drive a prey population to elimination. Initially, such studies require more reliable methods to count these cells. Flow cytometry (FCM) is potentially a rapid, accurate, and inexpensive tool for this, but it has yet to be validated for predatory bacteria. This study develops a protocol to count the predatory bacteria Bdellovibrio bacteriovorus and its Pseudomonas prey using FCM and compare the results with those of other methods, demonstrating its ability for studies into B. bacteriovorus predation dynamics. This could lead to the use of B. bacteriovorus for killing bacterial biofilms in fields, such as drinking water and agriculture.

Aims: The Mediterranean fruit fly (the medfly) causes major losses of agricultural fruits. Its microbiome is mainly composed of various Enterobacteriaceae that contribute to nutrient acquisition and are associated with the fly's development. Moreover, the performance of males produced by the sterile insect technique is improved by providing mass‐reared insects with specific gut bacteria. Bdellovibrio and like organisms (BALOs) are obligate predators of Gram‐negative bacteria that efficiently preys upon diverse Enterobacteriaceae, making it a potential disruptor of the fly's microbiome. We hypothesized that the fly's microbiome can be targeted to control the insect. Methods and Results: Inoculation of B. bacteriovorus as free‐swimming or encapsulated cells into gut extracts significantly reduced gut bacterial abundance, sustaining predator survival. Similar treatments applied to adult flies showed that the predators also survived in the gut environment. While addition of the predators did not affect total gut bacterial abundance and end‐point fly mortality, a shift in the gut community structure, measured by high‐throughput community sequencing was observed. Conclusions: The bacterial predator of bacteria B. bacteriovorus can prey and survive in vivo in the medfly gut. Significance and Impact of the Study: This study establishes the potential of BALOs to affect the microbiome of insect hosts. [ABSTRACT FROM AUTHOR]

Identified as a newly described species from a biocrust in Svalbard, Norway (78° 54' 8.27″ N 12° 01' 20.34″ E), isolate PAP01 T has different characteristics from any known predatory bacteria. The isolate was vibrio-shaped strain that employed flagellar motility. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate clustered within the genus Bdellovibrio in the family Bdellovibrionaceae . 16S rRNA gene sequence similarities between strain PAP01 T and the type strain ( Bdellovibrio bacteriovorus HD100) was 95.7 %. The PAP01 T genome has a size of 3.898 Mbp and possesses 3732 genes and a G+C content of 45.7 mol%. The results of genetic and physiological tests indicated the phenotypic differentiation of strain PAP01 T from the two other Bdellovibrio species with validly published names. Based on the physiological and phylogenetic data, as well as the prey range spectrum and osmolality sensitivities, isolate PAP01 T represents a novel species within the genus Bdellovibrio , for which the name Bdellovibrio svalbardensis sp. nov. is proposed. The type strain is PAP01 T (=KCTC 92583 T =DSM 115080 T ).

Objective(s): Bdellovibrio-and-like organisms (BALOs) are predatory prokaryotes that attack and kill other Gram-negative bacteria for growth and reproduction. This study describes the isolation, identification, biological properties, and bacteriolytic activity of the first Bdellovibrio bacteriovorus with a broad prey range from Iran. Materials and Methods: One BALO strain with high predatory potency was isolated from the rhizosphere soil using Enteropathogenic Escherichia coli as prey. It was identified and designated as Bdellovibrio bacteriovorus strain SOIR-1 through plaque assays, transmission electron microscopy (TEM), Bdellovibrio-specific PCRs, and 16S rRNA gene sequence analysis. Biological characterization and analysis of bacteriolytic activity were also performed. Results: TEM and Bdellovibrio-specific PCRs confirmed that the strain SOIR-1 belongs to the genus Bdellovibrio. Analysis of the 16S rRNA gene sequence revealed its close phylogenetic relationship with strains of Bdellovibrio bacteriovorus. The strain SOIR-1 grew within the temperature range of 25-37 °C and the pH range of 6.0-8.0, with the optimal predatory activity at 30 °C and pH 7.4. It had the highest and lowest bacteriolytic activity toward Shigella dysenteriae and Pseudomonas aeruginosa with a killing rate of 89.66% and 74.83%, respectively. Conclusion: Considering the hypothesis of bdellovibrios heterogeneity, identification of new isolates contributes to a deeper understanding of their diversity, their ecological roles, and their promising potential as living antibiotics or biocontrol agents. Bdellovibrios with broad bacteriolytic nature has not previously been reported in sufficient detail from Iran. The results of this study showed the great potential of native B. bacteriovorus strain SOIR-1 in the control and treatment of diseases caused by pathogenic Enterobacteriaceae. [ABSTRACT FROM AUTHOR]

The predatory bacterium B. bacteriovorus grows and divides inside the periplasm of Gram-negative bacteria, forming a structure known as a bdelloplast. Cell division of predators inside the dead prey cell is not by binary fission but instead by synchronous division of a single elongated filamentous cell into odd or even numbers of progeny cells. Bdellovibrio replication and cell division processes are dependent on the finite level of nutrients available from inside the prey bacterium. The filamentous growth and division process of the predator maximizes the number of progeny produced by the finite nutrients in a way that binary fission could not. To learn more about such an unusual growth profile, we studied the role of DivIVA in the growing Bdellovibrio cell. This protein is well known for its link to polar cell growth and spore formation in Gram-positive bacteria, but little is known about its function in a predatory growth context. We show that DivIVA is expressed in the growing B. bacteriovorus cell and controls cell morphology during filamentous cell division, but not the number of progeny produced. Bacterial Two Hybrid (BTH) analysis shows DivIVA may interact with proteins that respond to metabolic indicators of amino-acid biosynthesis or changes in redox state. Such changes may be relevant signals to the predator, indicating the consumption of prey nutrients within the sealed bdelloplast environment. ParA, a chromosome segregation protein, also contributes to bacterial septation in many species. The B. bacteriovorus genome contains three ParA homologs; we identify a canonical ParAB pair required for predatory cell division and show a BTH interaction between a gene product encoded from the same operon as DivIVA with the canonical ParA. The remaining ParA proteins are both expressed in Bdellovibrio but are not required for predator cell division. Instead, one of these ParA proteins coordinates gliding motility, changing the frequency at which the cells reverse direction. Our work will prime further studies into how one bacterium can co-ordinate its cell division with the destruction of another bacterium that it dwells within.

The affordability of next generation sequencing (NGS) is transforming the field of mutation analysis in bacteria. The genetic basis for phenotype alteration can be identified directly by sequencing the entire genome of the mutant and comparing it to the wild-type (WT) genome, thus identifying acquired mutations. A major limitation for this approach is the need for an a-priori sequenced reference genome for the WT organism, as the short reads of most current NGS approaches usually prohibit de-novo genome assembly. To overcome this limitation we propose a general framework that utilizes the genome of relative organisms as mediators for comparing WT and mutant bacteria. Under this framework, both mutant and WT genomes are sequenced with NGS, and the short sequencing reads are mapped to the mediator genome. Variations between the mutant and the mediator that recur in the WT are ignored, thus pinpointing the differences between the mutant and the WT. To validate this approach we sequenced the genome of Bdellovibrio bacteriovorus 109J, an obligatory bacterial predator, and its prey-independent mutant, and compared both to the mediator species Bdellovibrio bacteriovorus HD100. Although the mutant and the mediator sequences differed in more than 28,000 nucleotide positions, our approach enabled pinpointing the single causative mutation. Experimental validation in 53 additional mutants further established the implicated gene. Our approach extends the applicability of NGS-based mutant analyses beyond the domain of available reference genomes.

The predatory bacterium B. bacteriovorus grows and divides inside the periplasm of Gram-negative bacteria, forming a structure known as a bdelloplast. Cell division of predators inside the dead prey cell is not by binary fission but instead by synchronous division of a single elongated filamentous cell into odd or even numbers of progeny cells. Bdellovibrio replication and cell division processes are dependent on the finite level of nutrients available from inside the prey bacterium. The filamentous growth and division process of the predator maximizes the number of progeny produced by the finite nutrients in a way that binary fission could not. To learn more about such an unusual growth profile, we studied the role of DivIVA in the growing Bdellovibrio cell. This protein is well known for its link to polar cell growth and spore formation in Gram-positive bacteria, but little is known about its function in a predatory growth context. We show that DivIVA is expressed in the growing B. bacteriovorus cell and controls cell morphology during filamentous cell division, but not the number of progeny produced. Bacterial Two Hybrid (BTH) analysis shows DivIVA may interact with proteins that respond to metabolic indicators of amino-acid biosynthesis or changes in redox state. Such changes may be relevant signals to the predator, indicating the consumption of prey nutrients within the sealed bdelloplast environment. ParA, a chromosome segregation protein, also contributes to bacterial septation in many species. The B. bacteriovorus genome contains three ParA homologs; we identify a canonical ParAB pair required for predatory cell division and show a BTH interaction between a gene product encoded from the same operon as DivIVA with the canonical ParA. The remaining ParA proteins are both expressed in Bdellovibrio but are not required for predator cell division. Instead, one of these ParA proteins coordinates gliding motility, changing the frequency at which the cells reverse direction. Our work will prime further studies into how one bacterium can co-ordinate its cell division with the destruction of another bacterium that it dwells within. [ABSTRACT FROM AUTHOR]

Bacterial soft rot diseases caused by Pectobacterium spp. and Dickeya spp. affect a wide range of crops, including potatoes, a major food crop. As of today, farmers mostly rely on sanitary practices, water management, and plant nutrition for control. We tested the bacterial predators Bdellovibrio and like organisms (BALOs) to control potato soft rot. BALOs are small, motile predatory bacteria found in terrestrial and aquatic environments. They prey on a wide range of Gram-negative bacteria, including animal and plant pathogens. To this end, BALO strains HD100, 109J, and a ΔmerRNA derivative of HD100 were shown to efficiently prey on various rot-causing strains of Pectobacterium and Dickeya solani. BALO control of maceration caused by a highly virulent strain of Pectobacterium carotovorum subsp. brasilense was then tested in situ using a potato slice assay. All BALO strains were highly effective at reducing disease, up to complete prevention. Effectivity was concentration dependent, and BALOs applied before P. carotovorum subsp. brasilense inoculation performed significantly better than those applied after the disease-causing agent, maybe due to in situ consumption of glucose by the prey, as glucose metabolism by live prey bacteria was shown to prevent predation. Dead predators and the supernatant of BALO cultures did not significantly prevent maceration, indicating that predation was the major mechanism for the prevention of the disease. Finally, plastic resistance to predation was affected by prey and predator population parameters, suggesting that population dynamics affect prey response to predation. [ABSTRACT FROM AUTHOR]

Biodiversity is generally believed to be a main determinant of ecosystem functioning. This principle also applies to the microbiome and could consequently contribute to host health. According to ecological theory, communities are shaped by top predators whose direct and indirect interactions with community members cause stability and diversity. Bdellovibrio and like organisms (BALOs) are a neglected group of predatory bacteria that feed on Gram-negative bacteria and can thereby influence microbiome composition. We asked whether BALOs can predict biodiversity levels in microbiomes from distinct host groups and environments. We demonstrate that genetic signatures of BALOs are commonly found within the 16S rRNA reads from diverse host taxa. In many cases, their presence, abundance, and especially richness are positively correlated with overall microbiome diversity. Our findings suggest that BALOs can act as drivers of microbial alpha-diversity and should therefore be considered candidates for the restoration of microbiomes and the prevention of dysbiosis. [ABSTRACT FROM AUTHOR]

Bdellovibrio has shown promising potential as a "living antibiotic" in aquaculture due to its predatory nature towards bacteria. However, limited research has been conducted on the impact of Bdellovibrio on fish microbiota distribution and whether these effects are beneficial to the fish. This study aimed to investigate the effects of introducing Bdellovibrio into the aquaculture water of Carassius auratus for a two-month period, focusing on growth, survival rates, and gill microbiota distribution. The results revealed that the addition of Bdellovibrio significantly decreased the number of culturable bacteria in the water (P < 0.05) and improved the survival rates of C. auratus (P < 0.05). However, it had no significant impact on the fish's body weight gain rate (WGR) or specific growth rate (SGR). Microbiome 16S sequencing demonstrated a significant presence of Bdellovibrionota in the experimental group, which was absent in the control group. At the phyla level, Bdellovibrio had a notable influence on the distribution of microbial communities, particularly on Proteobacteria, Bacteroidota, Actinobacteriota, Verrucomicrobiota, and Deinococcota (P < 0.05). Additionally, the addition of Bdellovibrio reduced the abundance of Enterobacterales bacteria, as indicated by LEfSE analysis. The presence of Bdellovibrio in the gills of the experimental group was confirmed through PCR and qPCR detection. Furthermore, the Kaplan-Meier survival curves of C. auratus following immersion infections of Aeromonas hydrophila demonstrated effective protection when Bdellovibrio was added. In conclusion, these findings suggest that Bdellovibrio can serve as a substitute for antibiotics and positively influence microbial communities, ultimately benefiting the healthy growth of C. auratus. This study highlights the immense potential of Bdellovibrio as an antibiotic alternative in aquaculture. • The addition of Bdellovibrio to water significantly reduced the number of culturable bacteria in the water. • The Bdellovibrio could significantly increase the survival rates of crucian carps. • The Bdellovibrio can be obviously detected on foregut, midgut, hindgut and gills after long-term addition. • The Bdellovibrio can reduce the number of Enterobacterales bacteria. • The Bdellovibrio exhibit effectively protections of C. auratus after Aeromonas hydrophila immersion infections. [ABSTRACT FROM AUTHOR]

It was previously demonstrated that predatory bacteria are able to efficiently eliminate Gram-negative pathogens including antibiotic-resistant and biofilm-associated bacteria. In this proof-of-concept study we evaluated whether two species of predatory bacteria, Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus, were able to alter the survival of Gram-negative pathogens on the ocular surface. Clinical keratitis isolates of Pseudomonas aeruginosa (strain PAC) and Serratia marcescens (strain K904) were applied to the ocular surface of NZW rabbits followed by application of predatory bacteria. At time intervals, surviving pathogenic bacteria were enumerated. In addition, B. bacteriovorus and S. marcescens were applied to porcine organ culture corneas under contact lenses, and the ocular surface was examined by scanning electron microscopy. The ocular surface epithelial layer of porcine corneas exposed to S. marcescens, but not B. bacteriovorus was damaged. Using this model, neither pathogen could survive on the rabbit ocular surface for longer than 24 h. M. aeruginosavorus correlated with a more rapid clearance of P. aeruginosa but not S. marcescens from rabbit eyes. This study supports previous evidence that predatory bacteria are well tolerated by the cornea, but suggest that predatory bacteria do not considerably change the ability of the ocular surface to clear the tested Gram-negative bacterial pathogens from the ocular surface.

Abstract In this study, two strains of Bdellovibrio were isolated from soil samples using the culture‐dependent technique and two members of the family Enterobacteriaceae (Klebsiella sp. and Salmonella sp.) as prey. The Bdellovibrio strains were bacteriolytic, plaque‐forming, and highly motile gram‐negative bacteria. We identified and confirmed the Bdellovibrio strains using microscopy, PCR amplification, and sequencing of the 16S rRNA gene. They were observed to be different strains based on hit locus and prey range analyses. Here, the first report on Bdellovibrio strains isolated from soil in Mexico corroborates earlier report indicating that populations of Bdellovibrio found in soil are heterogeneous thereby the need to identify the various strains.

Ample evidence shows dysbiosis in the gut microbiota when comparing healthy shrimp with those affected by severe acute hepatopancreatic necrosis disease (AHPND). However, the static comparison used in available studies leads to the uncertainties regarding how and to what extent the gut microbiota responds to the progressive severity of AHPND. In addition, shrimp AHPND is featured by rapid and massive mortality, thus the initiation of AHPND must be diagnosed for preemptive therapy. For these reasons, we explored the ecological assembly of gut microbiota over shrimp AHPND progression. Increasing AHPND severity was associated with linear increase in the copies of pirAB genes, relative abundance of gut Vibrio and potentially pathogenic, and reduction in the gut bacterial diversity, stability, and relative abundance of Bdellovibrio. Negative and significant association between gut Vibrio and Bdellovibrio were noted, indicating that compromised predation exerts a role in AHPND progression. Notably, the extents of departure to the healthy shrimp gut microbiota were positively coupled with the increasing severity of AHPND. After controlling the temporal variation in the gut microbiota as healthy shrimp age, we constructed a diagnosis model that accurately diagnosed the initial, progressed or moribund stages of AHPND, with an overall accuracy of 86.5%. Shrimp AHPND induced more stochastic gut microbiotas as a consequence of the attenuated ability of diseased shrimp to select their commensals, resulting in convergent bacterial communities between gut and rearing water over AHPND progression. Collectively, our findings provide important step toward the ecological assembly of gut microbiota implicating in AHPND etiology and in diagnosing AHPND stages. KEY POINTS: • The departure of shrimp gut microbiota positively linked with AHPND severity. • The diagnosis model accurately diagnosed the stages of AHPND. • Shrimp AHPND induced more stochastic gut microbiota., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The use of bdellovibrios has been regarded as an alternative to control multidrug-resistant pathogens and fish bacteriosis. However, scarce information is available on the potential of bdellovibrios in the presence of copper sulfate, which is an algicide widely used to treat cyanobacterial blooms in aquaculture. In the present study, the effects of copper sulfate at sublethal and lethal levels (0.1 and 1.0 mg·L−1) on Bdellovibrio sp. strain BDF-H16 were evaluated. The growth of Bdellovibrio sp. strain BDF-H16 was significantly promoted by both concentrations of copper sulfate, but less so by the lethal concentration. The bacteriolysis of gibel carp-pathogenic Aeromonas hydrophila by Bdellovibrio sp. strain BDF-H16 was also stimulated by copper sulfate in both solid and liquid media. However, Bdellovibrio sp. strain BDF-H16 with 0.1 mg·L−1 copper sulfate clearly inhibited infection of gibel carps by A. hydrophila better than Bdellovibrio sp. strain BDF-H16 with 1.0 mg·L−1 copper sulfate did. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To detect marine Bdellovibrio and like organisms (BALOs) which are able to infect Vibrio parahaemolyticus from seawater of the Adriatic, Italy. To test, prey specificity and predation efficiency of our Halobacteriovorax isolate, named HBXCO1, towards 17 Vibrio and 7 non‐Vibrio strains linked to the Adriatic sea, Italy. Methods and Results: Double layer agar plating technique was used to enumerate BALOs and to evaluate their prey specificity and predation efficiency. Transmission electron microscopy and 16S rRNA analysis were used to identify them. Means of BALOs counts ranged from 5·0 PFU per ml (March 2017) to 98·6 PFU per ml (August 2016). HBXCO1 had the ability to attack all tested prey strains of V. parahaemolyticus, Vibrio cholerae non‐O1/O139 and Vibrio vulnificus, but it did not prey on non‐Vibrio strains and V. alginolyticus under the tested conditions. Conclusions: Bdellovibrio and like organisms capable of infecting pathogenic vibrios are naturally present in seawater of the Adriatic, Italy. Isolate HBXCO1 shows prey specificity preferentially for the Vibrio genus and high predatory efficiency towards a wide range of pathogenic strains. Significance and Impact of the Study: The public impact of V. parahaemolyticus, non‐O1/O139 V. cholerae and V. vulnificus in bivalves is relevant and current decontamination processes are not always effective. We believe that the predator HBXCO1 represents a potential candidate for the development of strategies of biocontrol of pathogenic vibrios in bivalves from harvesting to trade. [ABSTRACT FROM AUTHOR]

Select Agents are microorganisms and toxins considered to be exploitable as biological weapons. Although infections by many Select Agents can be treated by conventional antibiotics, the risk of an emerging or engineered drug resistant strain is of great concern. One group of microorganisms that is showing potential to control drug resistant Gram-negative bacteria are the predatory bacteria from the genera Bdellovibrio spp. and Micavibrio spp. In this study, we have examined the ability of Bdellovibrio bacteriovorus (B. bacteriovorus) strain 109J, HD100 and Micavibrio aeruginosavorus (M. aeruginosavorus) ARL-13 to prey on a variety of Select Agents. Our findings demonstrate that B. bacteriovorus and M. aeruginosavorus are able to prey efficiently on Yersinia pestis and Burkholderia mallei. Modest predation was also measured in co-cultures of B. bacteriovorus and Francisella tularensis. However, neither of the predators showed predation when Burkholderia pseudomallei and Brucella melitensis were used as prey.

ABSTRACT Cystic fibrosis (CF) lung microbiota composition has recently been redefined by the application of next-generation sequencing (NGS) tools, identifying, among others, previously undescribed anaerobic and uncultivable bacteria. In the present study, we monitored the fluctuations of this ecosystem in 15 CF patients during a 1-year follow-up period, describing for the first time, as far as we know, the presence of predator bacteria in the CF lung microbiome. In addition, a new computational model was developed to ascertain the hypothetical ecological repercussions of a prey-predator interaction in CF lung microbial communities. Fifteen adult CF patients, stratified according to their pulmonary function into mild (n = 5), moderate (n = 9), and severe (n = 1) disease, were recruited at the CF unit of the Ramón y Cajal University Hospital (Madrid, Spain). Each patient contributed three or four induced sputum samples during a 1-year follow-up period. Lung microbiota composition was determined by both cultivation and NGS techniques and was compared with the patients’ clinical variables. Results revealed a particular microbiota composition for each patient that was maintained during the study period, although some fluctuations were detected without any clinical correlation. For the first time, Bdellovibrio and Vampirovibrio predator bacteria were shown in CF lung microbiota and reduced-genome bacterial parasites of the phylum Parcubacteria were also consistently detected. The newly designed computational model allows us to hypothesize that inoculation of predators into the pulmonary microbiome might contribute to the control of chronic colonization by CF pathogens in early colonization stages. IMPORTANCE The application of NGS to sequential samples of CF patients demonstrated the complexity of the organisms present in the lung (156 species) and the constancy of basic individual colonization patterns, although some differences between samples from the same patient were observed, probably related to sampling bias. Bdellovibrio and Vampirovibrio predator bacteria were found for the first time by NGS as part of the CF lung microbiota, although their ecological significance needs to be clarified. The newly designed computational model allows us to hypothesize that inoculation of predators into the lung microbiome can eradicate CF pathogens in early stages of the process. Our data strongly suggest that lower respiratory microbiome fluctuations are not necessarily related to the patient’s clinical status.

The bacterial predator Bdellovibrio bacteriovorus is a model for the wider phenomenon of bacteria:bacteria predation, and the specialization required to achieve a lifestyle dependent on prey consumption. Bdellovibrio bacteriovorus is able to recognize, enter and ultimately consume fellow Gram-negative bacteria, killing these prey from within their periplasmic space, and lysing the host at the end of the cycle. The classic phenotype-driven characterization (and observation of predation) has benefitted from an increased focus on molecular mechanisms and fluorescence microscopy and tomography, revealing new features of several of the lifecycle stages. Herein we summarize a selection of these advances and describe likely areas for exploration that will push the field toward a more complete understanding of this fascinating 'two-cell' system.

Abstract: Aims: (i) To obtain and identify the predatory bacteria for the control of contaminated bacteria and to promote the autotrophic growth of Chlorella USTB‐01. (ii) To identify and measure the different cell numbers in microalgal culture using flow cytometer. Methods and Results: A predatory bacterial strain was isolated using Escherichia coli BL21 as a sole prey host, which was identified as Bdellovibrio USTB‐06 by the analysis of 16S rDNA sequence. A flow cytometer was successfully used to identify and measure the cell numbers of Chlorella USTB‐01, the contaminated bacteria and Bdellovibrio USTB‐06 simultaneously in the autotrophic culture of Chlorella USTB‐01 according to the identification of the different cell sizes. With the addition of Bdellovibrio USTB‐06 at initial 104 plaque‐forming units per ml, the contaminated bacteria severely decreased by about five counts (in log10 CFU per ml) and the growth of Chlorella USTB‐01 was greatly increased by 37·0% compared with those of control respectively. Conclusions: Bdellovibrio USTB‐06 could effectively promote the growth of Chlorella USTB‐01 via the killing of the contaminated bacteria. Significance and Impact of the Study: Our study reveals a good biotechnology method to increase the growth of Chlorella USTB‐01 which is very important in the industry of microalgal culture. [ABSTRACT FROM AUTHOR]

Bdellovibrio spp. are predatory bacteria with great potential as antimicrobial agents. Studies have shown that members of the genus Bdellovibrio exhibit peculiar characteristics that influence their ecological adaptations. In this study, whole genomes of two different Bdellovibrio spp. designated SKB1291214 and SSB218315 isolated from soil were sequenced. The core genes shared by all the Bdellovibrio spp. considered for the pangenome analysis including the epibiotic B. exovorus were 795. The number of unique genes identified in Bdellovibrio spp. SKB1291214, SSB218315, W, and B. exovorus JJS was 1343, 113, 857, and 1572, respectively. These unique genes encode hydrolytic, chemotaxis, and transporter proteins which might be useful for predation in the Bdellovibrio strains. Furthermore, the two Bdellovibrio strains exhibited differences based on the % GC content, amino acid identity, and 16S rRNA gene sequence. The 16S rRNA gene sequence of Bdellovibrio sp. SKB1291214 shared 99% identity with that of an uncultured Bdellovibrio sp. clone 12L 106 (a pairwise distance of 0.008) and 95–97% identity (a pairwise distance of 0.043) with that of other culturable terrestrial Bdellovibrio spp., including strain SSB218315. In Bdellovibrio sp. SKB1291214, 174 bp sequence was inserted at the host interaction (hit) locus region usually attributed to prey attachment, invasion, and development of host independent Bdellovibrio phenotypes. Also, a gene equivalent to Bd0108 in B. bacteriovorus HD100 was not conserved in Bdellovibrio sp. SKB1291214. The results of this study provided information on the genetic characteristics and diversity of the genus Bdellovibrio that can contribute to their successful applications as a biocontrol agent. [ABSTRACT FROM AUTHOR]

In this study, the removal of nutrients and chlorpyrifos as well as shifts of planktonic bacterial communities in constructed microcosms were investigated to evaluate the influence of Phragmites australis , Nymphaea alba , and Myriophyllum verticillatum , and their combination, on the restoration of eutrophic water containing chlorpyrifos. Plant-treated groups showed a higher pollutant removal rate than did no-remediation controls, indicating that treatment with plants is effective at remediation of eutrophic water containing chlorpyrifos. Different plants showed different performance on the remediation of eutrophic water, e.g., P. australis manifested stronger capacity for removal of sediment chlorpyrifos. This finding indicated that an appropriate plant combination is needed to deal with complex wastewater. During the treatments, the planktonic bacterial communities were influenced by the concentrations of nutrients and pollutants. The changes of composition of bacterial communities indicated a strong correlation between the bacterial communities and the concentrations of pollutants. The plants also influenced the planktonic bacterial communities, especially at the early phase of treatments. For example, P. australis increased the abundance of Limnohabitans and Nevskia significantly and decreased the abundance of Devosia , Luteolibacter , Methylibium , and Caulobacter significantly. The abundance of Hydrocarboniphaga significantly increased in N. alba -treated microcosms, whereas in M. verticillatum -treated microcosms, the abundance of Limnohabitans and Bdellovibrio significantly increased. Our results suggest that the planktonic bacterial communities may be altered during phytoremediation, and the functions of the affected bacteria should be concerned. [ABSTRACT FROM AUTHOR]