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Key message S29 haplotype does not require the MLPK function for self-incompatibility in Brassica rapa. Abstract Self-incompatibility (SI) in Brassicaceae is regulated by the self-recognition mechanism, which is based on the S-haplotype-specific direct interaction of the pollen-derived ligand, SP11/SCR, and the stigma-side receptor, SRK. M locus protein kinase (MLPK) is known to be one of the positive effectors of the SI response. MLPK directly interacts with SRK, and is phosphorylated by SRK in Brassica rapa. In Brassicaceae, MLPK was demonstrated to be essential for SI in B. rapa and Brassica napus, whereas it is not essential for SI in Arabidopsis thaliana (with introduced SRK and SP11/SCR from related SI species). Little is known about what determines the need for MLPK in SI of Brassicaceae. In this study, we investigated the relationship between S-haplotype diversity and MLPK function by analyzing the SI phenotypes of different S haplotypes in a mlpk/mlpk mutant background. The results have clarified that in B. rapa, all the S haplotypes except the S29 we tested need the MLPK function, but the S29 haplotype does not require MLPK for the SI. Comparative analysis of MLPK-dependent and MLPK-independent S haplotype might provide new insight into the evolution of S-haplotype diversity and the molecular mechanism of SI in Brassicaceae.

Background and purpose Fear of falling is associated with poor physical health and influences postural stability during whole-body movement. The ability to recover from lateral balance loss is required to prevent falls; however, the relationship between lateral balance recovery and fear of falling has not been established. This study aimed to investigate whether fear of falling is associated with the stepping threshold for lateral balance recovery. Methods This study included 56 ambulatory, community-dwelling women aged 65 years or older. We determined the single-step threshold as the maximum lean magnitude normalized with body weight from which participants could be suddenly released and still recover balance using a single side step. The short-form Falls Efficacy Scale International was used as a measure of fear of falling. Results and discussion The single-step threshold significantly correlated with age (rs = -0.603) and the short-form Falls Efficacy Scale International score (rs = -0.439). Ordinal regression analysis revealed that age (odds ratio, 0.826; 95% confidence interval, 0.742-0.920) and the short-form Falls Efficacy Scale International score (odds ratio, 0.811; 95% confidence interval, 0.680-0.966) were significantly associated with the single-step threshold, such that older age and greater fear of falling each independently predicted that failure to recover balance with a single step would occur at a lower percentage of body weight. Conclusions Greater fear of falling was associated with reduced ability to recover from lateral balance loss in addition to aging. Future studies should explore whether evidence-based interventions to reduce fear of falling combined with perturbation training might lead to improved ability to recover from balance loss.

Black band disease (BBD) in corals is characterized by a distinctive, band-like microbial mat, which spreads across the tissues and often kills infected colonies. The microbial mat is dominated by cyanobacteria but also commonly contains sulfide-oxidizing bacteria (SOB), sulfate-reducing bacteria (SRB), and other microbes. The migration rate in BBD varies across different environmental conditions, including temperature, light, and pH. However, whether variations in the migration rates reflect differences in the microbial consortium within the BBD mat remains unknown. Here, we show that the micro-scale surface structure, bacterial composition, and spatial distribution differed across BBD lesions with different migration rates. The migration rate was positively correlated with the relative abundance of potential SOBs belonging to Arcobacteraceae localized in the middle layer within the mat and negatively correlated with the relative abundance of other potential SOBs belonging to Rhodobacteraceae. Our study highlights the microbial composition in BBD as an important determinant of virulence.

Background Many animals live in intimate associations with a species-rich microbiome. A key factor in maintaining these beneficial associations is fidelity, defined as the stability of associations between hosts and their microbiota over multiple host generations. Fidelity has been well studied in terrestrial hosts, particularly insects, over longer macroevolutionary time. In contrast, little is known about fidelity in marine animals with species-rich microbiomes at short microevolutionary time scales, that is at the level of a single host population. Given that natural selection acts most directly on local populations, studies of microevolutionary partner fidelity are important for revealing the ecological and evolutionary processes that drive intimate beneficial associations within animal species. Results In this study on the obligate symbiosis between the gutless marine annelid Olavius algarvensis and its consortium of seven co-occurring bacterial symbionts, we show that partner fidelity varies across symbiont species from strict to absent over short microevolutionary time. Using a low-coverage sequencing approach that has not yet been applied to microbial community analyses, we analysed the metagenomes of 80 O. algarvensis individuals from the Mediterranean and compared host mitochondrial and symbiont phylogenies based on single-nucleotide polymorphisms across genomes. Fidelity was highest for the two chemoautotrophic, sulphur-oxidizing symbionts that dominated the microbial consortium of all O. algarvensis individuals. In contrast, fidelity was only intermediate to absent in the sulphate-reducing and spirochaetal symbionts with lower abundance. These differences in fidelity are likely driven by both selective and stochastic forces acting on the consistency with which symbionts are vertically transmitted. Conclusions We hypothesize that variable degrees of fidelity are advantageous for O. algarvensis by allowing the faithful transmission of their nutritionally most important symbionts and flexibility in the acquisition of other symbionts that promote ecological plasticity in the acquisition of environmental resources.

We compared the spatiotemporal characteristics of lateral perturbation-induced reactive stepping in stroke subjects with those of age-matched controls. We subjected 12 stroke subjects and 17 healthy elderly controls to lateral stepping. We analyzed first-step spatiotemporal parameters during stepping and recorded the selected reactive step types at the stepping threshold. Stroke subjects showed a lower stepping threshold and more frequently used medial steps than controls. Stroke subjects also had a longer delay prior to foot-off in lateral steps when perturbed toward the nonparetic side, and in medial steps when perturbed toward both sides than controls. Thus, the time deficits in reactive stepping in individuals with stroke may be attributed to stroke-related sensorimotor impairments, indicating their limitations in balance control.

The composition and diversity of animal microbiomes is shaped by a variety of factors, many of them interacting, such as host traits, the environment, and biogeography. Hybrid zones, in which the ranges of two host species meet and hybrids are found, provide natural experiments for determining the drivers of microbiome communities, but have not been well studied in marine environments. Here, we analysed the composition of the symbiont community in two deep-sea,Bathymodiolusmussel species along their known distribution range at hydrothermal vents on the Mid-Atlantic Ridge, with a focus on the hybrid zone where they interbreed. In-depth metagenomic analyses of the sulphur-oxidising symbionts of 30 mussels from the hybrid zone, at a resolution of single nucleotide polymorphism analyses of ~2500 orthologous genes, revealed that parental and hybrid mussels (F2–F4 generation) have genetically indistinguishable symbionts. While host genetics does not appear to affect symbiont composition in these mussels, redundancy analyses showed that geographic location of the mussels on the Mid-Atlantic Ridge explained most of the symbiont genetic variability compared to the other factors. We hypothesise that geographic structuring of the free-living symbiont population plays a major role in driving the composition of the microbiome in these deep-sea mussels.

[Purpose] Adults with cerebral palsy often use a cane as a walking aid because of their decreased gait ability. However, it is unclear whether this affects lower limb muscle activity during walking. The purpose of this study was to clarify the influence of using a cane during walking on the spatio-temporal parameters of walking, lower limb muscle activity, and lower limb muscle coactivation in adults with spastic cerebral palsy. [Participants and Methods] Eleven participants with cerebral palsy were included. The spatio-temporal parameters of walking, lower limb muscle activity, and coactivation of lower limb muscle were measured during a 10 m trial with no cane, one cane, and two canes. [Results] Walking speed was lower and the stride time longer when using two canes than when using no cane. All muscle activities significantly reduced when using two canes. No significant difference was observed between using no cane and one cane, except for walking speed. In addition, there was no significant difference in coactivation between the conditions. [Conclusion] This study revealed that when two canes were used, the walking speed was reduced, and lower limb muscle activity was reduced, reducing the burden. In contrast, the movement pattern was not suggested to have changed.

Eukaryotes may experience oxygen deprivation under both physiological and pathological conditions. Because oxygen shortage leads to a reduction in cellular energy production, all eukaryotes studied so far conserve energy by suppressing their metabolism. However, the molecular physiology of animals that naturally and repeatedly experience anoxia is underexplored. One such animal is the marine nematode Laxus oneistus. It thrives, invariably coated by its sulfur-oxidizing symbiont Candidatus Thiosymbion oneisti, in anoxic sulfidic or hypoxic sand. Here, transcriptomics and proteomics showed that, whether in anoxia or not, L. oneistus mostly expressed genes involved in ubiquitination, energy generation, oxidative stress response, immune response, development, and translation. Importantly, ubiquitination genes were also highly expressed when the nematode was subjected to anoxic sulfidic conditions, together with genes involved in autophagy, detoxification and ribosome biogenesis. We hypothesize that these degradation pathways were induced to recycle damaged cellular components (mitochondria) and misfolded proteins into nutrients. Remarkably, when L. oneistus was subjected to anoxic sulfidic conditions, lectin and mucin genes were also upregulated, potentially to promote the attachment of its thiotrophic symbiont. Furthermore, the nematode appeared to survive oxygen deprivation by using an alternative electron carrier (rhodoquinone) and acceptor (fumarate), to rewire the electron transfer chain. On the other hand, under hypoxia, genes involved in costly processes (e.g., amino acid biosynthesis, development, feeding, mating) were upregulated, together with the worm’s Toll-like innate immunity pathway and several immune effectors (e.g., Bacterial Permeability Increasing proteins, fungicides). In conclusion, we hypothesize that, in anoxic sulfidic sand, L. oneistus upregulates degradation processes, rewires oxidative phosphorylation and by reinforces its coat of bacterial sulfur-oxidizers. In upper sand layers, instead, it appears to produce broad-range antimicrobials and to exploit oxygen for biosynthesis and development.

Backhousia citriodora (lemon myrtle) extract has been found to inhibit glucansucrase activity, which plays an important role in biofilm formation by Streptococcus mutans. In addition to glucansucrase, various virulence factors in S. mutans are involved in the initiation of caries. Lactate produced by S. mutans demineralizes the tooth enamel. This study investigated whether lemon myrtle extract can inhibit S. mutans lactate production. Lemon myrtle extract reduced the glycolytic pH drop in S. mutans culture and inhibited lactate production by at least 46%. Ellagic acid, quercetin, hesperetin, and myricetin, major polyphenols in lemon myrtle, reduced the glycolytic pH drop and lactate production, but not lactate dehydrogenase activity. Furthermore, these polyphenols reduced the viable S. mutans cell count. Thus, lemon myrtle extracts may inhibit S. mutans-mediated acidification of the oral cavity, thereby preventing dental caries and tooth decay.

To closely mimic physiological conditions, low oxygen cultures have been employed in stem cell and cancer research. Although in vivo oxygen concentrations in tissues are often much lower than ambient 21% O2 (ranging from 3.6 to 12.8% O2), most cell cultures are maintained at 21% O2. To clarify the effects of the O2 culture concentration on the regulated secretion of peptide hormones in neuro-endocrine cells, we examined the changes in the storage and release of peptide hormones in neuro-endocrine cell lines and endocrine tissues cultured in a relatively lower O2 concentration. In both AtT-20 cells derived from the mouse anterior pituitary and freshly prepared mouse pituitaries cultured in 10% O2 for 24 h, the storage and regulated secretion of the mature peptide hormone adrenocorticotropic hormone were significantly increased compared with those in cells and pituitaries cultured in ambient 21% O2, whereas its precursor proopiomelanocortin was not increased in the cells and tissues after being cultured in 10% O2. Simultaneously, the prohormone-processing enzymes PC1/3 and carboxypeptidase E were up-regulated in cells cultured in 10% O2, thus facilitating the conversion of prohormones to their active form. Similarly, culturing the mouse β-cell line MIN6 and islet tissue in 10% O2 also significantly increased the conversion of proinsulin into mature insulin, which was secreted in a regulated manner. These results suggest that culture under 10% O2 is more optimal for endocrine tissues/cells to efficiently generate and secrete active peptide hormones than ambient 21% O2.

The measurement of Cs adsorption by the precipitation bands of Mn-based Prussian blue analogues (PBAs), Co-based PBAs, and Prussian blue (PB), which were spontaneously formed in agarose gel, was carried out using in situ X-ray fluorescence (XRF) spectroscopy. Three gel samples, namely “Mn-PBA,” “Co-PBA,” and “PB,” were prepared by bringing 0.05 M [Fe(CN)6]3− agarose gel (2.3 mass%) into contact with 0.50 M solutions of MnSO4, CoCl2, and FeCl2, respectively. Mn-PBA formed relatively wide, discrete precipitation bands, whereas Co-PBA and PB each formed a continuous band. The XRF intensity distribution measurements determined using an energy-dispersive XRF setup showed that the PBA/PB concentration fluctuates considerably in Mn-PBA but not in Co-PBA or PB. Time-dependent Cs L-emission distributions for these samples, into which a 0.10 M CsCl solution was introduced, indicated that in agarose gel, the precipitates of Mn-based PBAs can trap Cs+ more effectively than those of PB and Co-based PBAs if the Cs processing time is relatively long (i.e., ≥10 d). These results demonstrate the potential applicability of Mn-based PBA precipitates that are self-organized in agarose gel as pulsatile 137Cs adsorbent delivery materials.

Many animals are obligately associated with microbial symbionts that provide essential services such as nutrition or protection against predators. It is assumed that in such obligate associations fidelity between the host and its symbionts must be high to ensure the evolutionary success of the symbiosis. We show here that this is not the case in marine oligochaete worms, despite the fact that they are so dependent on their bacterial symbionts for their nutrition and waste recycling that they have lost their digestive and excretory systems. Our metagenomic analyses of 64 gutless oligochaete species from around the world revealed highly variable levels of fidelity not only across symbiont lineages, but also within symbiont clades. We hypothesize that in gutless oligochaetes, selection within host species for locally adapted and temporally stable symbiont communities leads to varying levels of symbiont fidelity and shuffles the composition of symbiont assemblages across geographic and evolutionary scales.

Here, we present two high-quality, draft metagenome-assembled genomes of deltaproteobacterial OalgDelta3 endosymbionts from the gutless marine worm Olavius algarvensis. Their 16S rRNA gene sequences share 98% identity with Delta3 endosymbionts of related host species Olavius ilvae (GenBank accession no. AJ620501) and Inanidrilus exumae (GenBank accession no. FM202060), for which no symbiont genomes are available.

Here, we present high-quality metagenome-assembled genome sequences of two closely related deltaproteobacterial endosymbionts from the gutless marine worm Olavius algarvensis (Annelida). The first is an improved draft genome sequence of the previously described sulfate-reducing symbiont Delta1. The second is from a closely related, recently discovered symbiont of O. algarvensis.

In Japan, most of H-shaped beams are rigidly connected to the box sectional columns which have high torsional rigidity, and the boundary condition is corresponding to warping fixed support. Our previous papers clarified that the lateral buckling load of beams with the warping restraint becomes higher than that with pinned support. Furthermore, it was shown that the continuous braces such as roof purlins or concrete slabs connected to the beams also prevent the lateral buckling deformation. This paper evaluates the restraint effect of continuous braces on the lateral buckling load for H-shaped beams with fork restraint under the uniform flexural moment. The lateral buckling load of beams with warping and fully fixed supports is estimated by formulating energy conservation equations. Next, this paper derives the equations of elastic lateral buckling load of beams with fork restraint, which is corresponding to the rotational restraint between warping and fully fixed supports by torsional resistance of column. By comparing the equations with the numerical analyses results, the restraint effect of the continuous braces and column on the lateral buckling is verified. It is shown that the lateral buckling stress becomes higher, as the rigidity of the continuous braces or fork restraint increases.

Research into causative agents underlying coral disease have focused primarily on bacteria, whereas potential roles of viruses have been largely unaddressed. Bacteriophages may contribute to diseases through the lysogenic introduction of virulence genes into bacteria, or prevent diseases through lysis of bacterial pathogens. To identify candidate phages that may influence the pathogenicity of black band disease (BBD), communities of bacteria (16S rRNA) and T4-bacteriophages (gp23) were simultaneously profiled with amplicon sequencing among BBD-lesions and healthy-coral-tissue of Montipora hispida, as well as seawater (study site: the central Great Barrier Reef). Bacterial community compositions were distinct among BBD-lesions, healthy coral tissue and seawater samples, as observed in previous studies. Surprisingly, however, viral beta diversities based on both operational taxonomic unit (OTU)-compositions and overall viral community compositions of assigned taxa did not differ statistically between the BBD-lesions and healthy coral tissue. Nonetheless, relative abundances of three bacteriophage OTUs, affiliated to Cyanophage PRSM6 and Prochlorococcus phages P-SSM2, were significantly higher in BBD-lesions than in healthy tissue. These OTUs associated with BBD samples suggest the presence of bacteriophages that infect members of the cyanobacteria-dominated BBD community, and thus have potential roles in BBD pathogenicity.

Increases in the frequency of perturbations that drive coral community structure, such as severe thermal anomalies and high intensity storms, highlight the need to understand how coral communities recover following multiple disturbances. We describe the dynamics of cover and assemblage composition of corals on exposed inshore reefs in the Palm Islands, central Great Barrier Reef, over 19 years encapsulating major disturbance events such as the severe bleaching event in 1998 and Cyclone Yasi in 2011, along with other minor storm and heat stress events. Over this time, 47.8% of hard coral cover was lost, with a concomitant shift in coral assemblage composition due to taxon-specific rates of mortality during the disturbances, and asymmetric recovery in the aftermath thereof. High recruitment rates of some broadcast-spawning corals, particularly corymbose Acropora spp., even in the absence of adult colonies, indicate that a strong external larval supply replenished the stocks. Conversely, the time required for recovery of slow-growing coral morphologies and life histories was longer than the recurrence times of major disturbances. With interludes between bleaching and cyclones predicted to decrease, the probability of another severe disturbance event before coral cover and assemblage composition approximates historical levels suggests that reefs will continue to erode.

This study was funded by a research grant from Mitsubishi Corporation and Earthwatch Australia. Data collection was supported by the citizen scientists who participated in the "Recovery of the Great Barrier Reef'' project organized by Earthwatch Australia. The authors wish to thank all volunteers (> 50) who contributed to the collection of data associated with the study. The authors also thank staff of James Cook University's Orpheus Island Research Station for their logistic support, Kathleen Morrow, Emmanuelle Botte, Nachshon Siboni, Brett Baillie, Andrew Muirhead, Naohisa Wada, Paul O'Brien, Lesa Peplow, Pedro Frade from AIMS and Sefano Katz, Gergely Torda, and Georgina Torras Jorda from Earthwatch for their support in field activities.

Inorganic precipitates sometimes spontaneously create complex, interesting banding structures in gels, which are potentially applicable in materials engineering. A new member of such self-organizing bandings, i.e., stochastic, periodic banding of the precipitates of Co–Fe-based Prussian blue analogues (Co–Fe PBAs), denoted as “pattern-A”, was observed in water-glass gels. The pattern-A periodic bands did not obey empirical scaling laws that many Liesegang bands follow, illustrating the importance of ripening effects. Time-resolved X-ray fluorescence (XRF) and position-dependent X-ray absorption near-edge structure (XANES) measurements were conducted for a pattern-A sample, which was prepared from 0.30 M CoCl2 and 0.05 M K3[Fe(CN)6] solutions. XRF results demonstrated that the Co–Fe PBA distributions fluctuated highly over the sample tube, including the turbid zone, and suggested that significant Ostwald ripening of the Co–Fe PBAs takes place in the periodic bands. XANES results indicated that the local structures and symmetries of the Co–Fe PBAs in the periodic bands were highly uniform. Furthermore these results are consistent with a model where the periodic bands contain a relatively high concentration of Co–Fe PBAs, with the most dominant local structure being Co(OC)4(NCFe)2, co-existing with [Co(H2O)6]2+ ions. These findings not only provide an interesting piece of information for future self-organization processes of Co–Fe PBAs, but also confirm the potential of the combined X-ray spectroscopic techniques for in-depth analysis of the periodic precipitation phenomenon in gels.

We report that submicron-sized, N-isopropyl acrylamide/acrylamide copolymer microgel particles crystallized in dilute aqueous solutions of poly(acrylamide) linear polymers, because of depletion int...

The browning or discoloration of cheese is often observed during long-time ripening or aging. In the present study, we identified galactose as a limiting factor for the browning, and clarified the involvement of the Maillard reaction for the discoloration. A precursor of browning of Cheddar cheese was isolated by procedures of solvent extraction and chromatography. D-Galactose and D-lactose were identified as a precursor of browning of Cheddar cheese A and B, respectively. Cheddar cheese (A, B, and C), sugar-added cheese, and nine kinds of retail cheese were stored at 4 to 70ºC for 0 to 10 d, before the L*-, a*-, and b*-values and sugar contents of each sample were measured. Cheese to which galactose was added turned brown more intensively during storage than the non-added control and the other sugar-added cheese. The more galactose was added, the more intensive the browning of the cheese appeared. The decrease in galactose correlated with the ΔL*-, Δa*-, Δb*-, and ΔE-values indicating the browning or discoloration of cheese samples. The decrease in sugars of nine kinds of retail cheese during storage also correlated with the ΔL*-, Δa*-, and ΔE-values of these cheese samples. These results clearly indicate that sugars, especially galactose, in cheese are an important factor for the browning of cheese during storage. In general, a high amount of amino acids, peptides, and proteins exists in ripe or mature cheese. Therefore, sugars, especially galactose, were considered to be the limiting factor for the Maillard reaction causing the browning of ripe or mature cheese during storage.

The adsorption of Cs+ ions by the precipitation bands of a Mn–Fe based Prussian blue analogue (Mn–Fe PBA) that form spontaneously in agarose gel was investigated by X-ray absorption fine structure spectroscopy coupled with scanning electron microscopy (SEM) and X-ray fluorescence (XRF) distribution analysis. Two gel samples were prepared by contacting a gel containing 0.05 M [Fe(CN)6]3− and 2.3 mass% agarose with a 0.50 M MnSO4 solution, into one of which a 0.10 M CsCl solution was introduced. The SEM images and the XRF intensity distributions reveal that Mn–Fe PBA forms cubic crystallites (approx. 3 × 3 × 3 μm in size) in the gels that trap Cs+ ions with considerably high affinity. Cs L3-edge and Mn K-edge X-ray absorption near-edge structure (XANES) spectra, which were analyzed with the aid of FEFF simulations, strongly suggest that Cs adsorption occurs at relatively large defect sites close to the sub-cube faces in the PBA. This suggestion is supported by Cs L3-edge extended X-ray absorption fine structure spectroscopy, which suggested that the first and second coordination shells around the Cs+ ions are at a Cs–O distance of 0.35 ± 0.02 nm and a Cs–N distance of 0.43 ± 0.01 nm, respectively, with coordination numbers of 1.5 ± 0.5 and 3.0 ± 0.5. The Mn K-edge XANES data also suggest that H2O molecules, which initially occupy many cubic centers in the Mn–Fe PBAs, are mostly displaced during Cs adsorption. These findings provide valuable insight toward fully understanding Cs adsorption by Mn–Fe PBA.

This study aimed to analyze the development of direction specificities of temporal and spatial control and the coordination pattern of anticipatory postural adjustment (APA) along the anteroposterior (AP) and mediolateral (ML) directions during gait initiation (GI) in children aged 3–10 years. This study included 72 healthy children aged 3–10 years and 14 young adults. The child population was divided into four groups by age: 3–4, 5–6, 7–8, and 9–10 years. The GI task included GI using the dominant limb. The peak center of feet pressure (COP) shifts during APAs (APApeak), initiation time of COP shifts (APAonset), and the COP vectors in the horizontal plane were calculated to evaluate the direction specificity of spatial, temporal, and coordination control, respectively. A difference in direction specificity development was found for the APApeak. The APApeak in the mediolateral axis, but not in the anteroposterior axis, was significantly higher in the 7–8 years age group than in other groups. Although APAonset was not found for direction specificity, a significant difference between the adult and children groups (5–6 years, 7–8 years, and 9–10 years) was observed in the direction of the COP vector. In conclusion, the developmental process of the spatial, temporal, and coordination control of APAs during GI varied with age. Furthermore, the spatial control and coordination pattern of APAs was found to be direction specific. All components of APAs, namely temporal and spatial control, coordination pattern, and direction specificities, should be analyzed to capture the developmental process of anticipatory postural control.

Emerging infectious diseases are contributing to global declines in coral reef ecosystems, highlighting a growing need for aetiological knowledge to develop effective management strategies. In this review, we focus on black band disease (BBD), one of the most virulent diseases and the only polymicrobial disease so far known to affect corals. A multipartite microbial consortium dominated by Cyanobacteria, but also including sulfur-cycling bacteria, other bacterial groups and members of the Archaea and Eukarya, forms a sulfide-rich anaerobic mat that migrates across the surface of coral colonies, killing the underlying tissues. The polymicrobial nature of the disease challenges classic aetiological approaches to unravelling disease causation. Here, we synthesize current knowledge on the range of pathogens forming the microbial consortium with recent studies on the transmission, biogeochemistry and environmental drivers of BBD to develop a conceptual model of BBD pathogenesis. The model illustrates how the development of BBD virulence factors is linked to a cascade of microbial community shifts and associated functional roles that progressively develop the microbial consortium from comparatively benign cyanobacterial patches to virulent BBD lesions. This review showcases how an approach that integrates multiple key aspects of the disease provides insights essential to elucidating the aetiology of BBD.

To closely mimic physiological conditions, low oxygen cultures have been employed in stem cell and cancer research. Although

This study investigated the diversity and quantitative shifts of sulfur-oxidizing bacteria (SOB) during the onset of black band disease (BBD) in corals using quantitative PCR (qPCR) and cloning approaches targeting the soxB gene, involved in sulfur oxidation. Four Montipora sp. coral colonies identified with lesions previously termed cyanobacterial patches (CP) (comprising microbial communities different from those of BBD lesions), was monitored in situ as CP developed into BBD. The overall abundance of SOB in both CP and BBD lesions were very low and near the detection limit of the qPCR assay, although consistently indicated that SOB populations decreased as the lesions transitioned from CP to BBD. Phylogenetic assessment of retrieved soxB genes showed that SOB in both CP and BBD lesions were dominated by one sequence type, representing > 70% of all soxB gene sequences and affiliated with members of the Rhodobacteraceae within the α-Proteobacteria. This study represents the first assessment targeting SOB within BBD lesions and clearly shows that SOB are not highly diverse or abundant in this complex microbial mat. The lack of oxidation of reduced sulfur compounds by SOB likely aids the accumulation of high levels of sulfide at the base of the BBD mat, a compound contributing to the pathogenicity of BBD lesions.

Seawater temperature anomalies associated with warming climate have been linked to increases in coral disease outbreaks that have contributed to coral reef declines globally. However, little is known about how seasonal scale variations in environmental factors influence disease dynamics at the level of individual coral colonies. In this study, we applied a multi-state Markov model (MSM) to investigate the dynamics of black band disease (BBD) developing from apparently healthy corals and/or a precursor-stage, termed ‘cyanobacterial patches’ (CP), in relation to seasonal variation in light and seawater temperature at two reef sites around Pelorus Island in the central sector of the Great Barrier Reef. The model predicted that the proportion of colonies transitioning from BBD to Healthy states within three months was approximately 57%, but 5.6% of BBD cases resulted in whole colony mortality. According to our modelling, healthy coral colonies were more susceptible to BBD during summer months when light levels were at their maxima and seawater temperatures were either rising or at their maxima. In contrast, CP mostly occurred during spring, when both light and seawater temperatures were rising. This suggests that environmental drivers for healthy coral colonies transitioning into a CP state are different from those driving transitions into BBD. Our model predicts that (1) the transition from healthy to CP state is best explained by increasing light, (2) the transition between Healthy to BBD occurs more frequently from early to late summer, (3) 20% of CP infected corals developed BBD, although light and temperature appeared to have limited impact on this state transition, and (4) the number of transitions from Healthy to BBD differed significantly between the two study sites, potentially reflecting differences in localised wave action regimes.

Coral disease outbreaks contribute to the ongoing degradation of reef ecosystems, however, microbial mechanisms underlying the onset and progression of most coral diseases are poorly understood. Black band disease (BBD) manifests as a cyanobacterial-dominated microbial mat that destroys coral tissues as it rapidly spreads over coral colonies. To elucidate BBD pathogenesis, we apply a comparative metagenomic and metatranscriptomic approach to identify taxonomic and functional changes within microbial lesions during in-situ development of BBD from a comparatively benign stage termed cyanobacterial patches. Results suggest that photosynthetic CO2-fixation in Cyanobacteria substantially enhances productivity of organic matter within the lesion during disease development. Photosynthates appear to subsequently promote sulfide-production by Deltaproteobacteria, facilitating the major virulence factor of BBD. Interestingly, our metagenome-enabled transcriptomic analysis reveals that BBD-associated cyanobacteria have a putative mechanism that enables them to adapt to higher levels of hydrogen sulfide within lesions, underpinning the pivotal roles of the dominant cyanobacterium within the polymicrobial lesions during the onset of BBD. The current study presents sequence-based evidence derived from whole microbial communities that unravel the mechanism of development and progression of BBD.

Histological observations represent an important application to directly characterize the structure of tissues and locate host-associated and invasive microorganisms. Histological approaches have been widely employed in studies of the physiology, pathology and ecology of corals. However, the conventional preparation of histological sections requires decalcification of coral samples to remove the hard skeletal structure in a series of acid or EDTA solutions over a weeks’ period, causing potential disturbances in coral structures on prepared slides. In this study, we present an alternative method to prepare thin sections from undecalcified frozen coral tissues, which has been developed for retaining the structural integrity of histological sections including skeleton. Cross sections of normal and diseased (rapid tissue necrosis and black band disease) coral specimens prepared with this method displayed the complete structure of the coral fragments including soft tissues and skeleton structure at microscopic scales, thereby clearly showing the orientation of damaged tissues and associated microorganisms in relation to skeletal structures. This study demonstrates that the present cryosectioning method without the need for decalcification is a highly effective tool for in-depth understanding of coral tissue/skeleton interactions.