Hasil untuk "Microbial ecology"

Chang-Xiao Shi, Ying-Qi Li, Shun-Ran Yang et al.

Heat stress (HS) poses a major threat to the beef cattle industry, causing significant economic losses. This study investigated the effects of yeast culture (YC) supplementation on HS mitigation, growth performance, and microbial modulation in late-fattening Angus steers. Twenty-seven steers (555.93 ± 22.39 kg BW, Mean ± SD) were randomly assigned to 3 groups: control (basal diet), low-dose YC (30 g/steer/d), and high-dose YC (60 g/steer/d) for 97 days. Two sampling time points were established: 30d (HS period) and 90d (recovery period). Results showed that 30 g/d YC significantly increased average daily gain (ADG) by 24.6% and reduced feed-to-gain ratio (F/G) by 19.7% compared with the control group during 0–90 d (P < 0.05). During HS, YC supplementation significantly elevated rectal temperature in steers within normal physiological ranges, but reduced respiratory rate during most periods (P < 0.05). YC supplementation elevated serum high-density lipoprotein cholesterol (P = 0.033), reduced low-density lipoprotein cholesterol (P = 0.046). A significant time effect was observed: the recovery period was accompanied by increased ruminal volatile fatty acids, elevated serum energy metabolites, and enhanced antioxidant enzyme activity (e.g., superoxide dismutase) (P < 0.05). Urinary creatinine (P = 0.024) and serum catalase levels (P = 0.096) varied with both YC dose and time. Microbiota analysis revealed that YC reshaped the ruminal and fecal communities by enriching fibrolytic bacteria, such as Ruminococcus, while simultaneously suppressing methanogens like Methanosphaera. We conclude that supplementing YC contributes to adaptation to HS by modulating glycolipid metabolism, antioxidant pathways, and microbial ecology. At the recommended dosage of 30 g/steer/d, YC supplementation enhances feed efficiency, improves farm profitability, and establishes a viable strategy for sustainable beef production.

Arkajyoti Ghoshal, Soumitree Mishra, Jayabrata Dhar et al.

ABSTRACT Diel vertical migration (DVM) is the daily movement of motile phytoplankton between light‐rich surface waters and deeper nutrient‐rich layers, typically governed by internal clocks. However, many species show irregular patterns that deviate from expected circadian rhythms. Studying Heterosigma akashiwo, a bloom‐forming phytoplankton, we found that cells regulate their vertical movement by modulating local pH, affecting their gravitactic behavior. This self‐regulation creates sub‐populations that are physiologically similar but differ in behavior, remaining vertically separated even in uniform environments. These sub‐populations had similar swimming speeds, growth, and photosynthetic activity, suggesting stable co‐existence rather than environmental differences. Remarkably, vertical separation reappeared when each group was exposed to the other's spent media—an effect not seen with their own. Modeling and imaging showed that these chemical cues subtly alter cell shape, influencing gravitactic stability. Further experiments confirmed that pH shifts, consistent with those in the spent media, could replicate these behavioral changes. Together with nighttime data, results support a circadian model where diurnal pH regulation drives gravitactic divergence. This chemically mediated migration may enhance ecological fitness by promoting division of labor across the day‐night cycle and could refine models of phytoplankton behavior, circadian, diel vertical migration, gravitaxis, microswimmers, modelling, pH particularly in the context of ocean acidification.

Romana Salis, Lars‐Anders Hansson

ABSTRACT Quantifications of phytoplankton biomass and species composition are crucial for monitoring biodiversity and population dynamics in aquatic environments, and both direct microscopic counts and fluorescence‐based methods have been widely used for monitoring. Recent advancements in DNA metabarcoding offer an alternative way of easily assessing diversity and species composition. However, a comprehensive comparison of the relative merits and limitations of DNA‐ and fluorescence‐based methods is currently lacking. Here we compare phytoplankton community composition measured via fluorescence and DNA metabarcoding in an outdoor, replicated mesocosm experiment. We show that there is a positive correlation between fluorescence‐measured biomass and DNA read and amplicon sequence variants (ASV) numbers for cyanobacteria, but either weak or no correlation for the other phytoplankton groups assessed (cryptophytes, chromophytes, and green algae). In addition, DNA metabarcoding was systematically better at detecting cryptophytes, which were rarely detected via fluorescence. Hence, while DNA metabarcoding may not provide reliable biomass estimates for the majority of phytoplankton groups, metabarcoding analysis offers higher taxonomic resolution and the capability to detect rare phytoplankton groups. Overall, our findings provide new insights into the strengths and limitations of each method and highlight the considerable potential and importance of including DNA barcoding in freshwater ecosystem assessment and biomonitoring programmes with a focus on biodiversity assessments.

Annette Brandt, Timur Yergaliyev, Emina Halibasic et al.

Summary: Dietary fiber enrichment may modulate intestinal microbiota and positively impact metabolic dysfunction-associated steatotic liver disease (MASLD). This randomized, double-blind, placebo-controlled dual-center study evaluated the effects of dietary fiber (oat bran and spelt bran) on MASLD. After a 3-week Run-in phase during which dietary intake was assessed, 48 patients (CAP >280 dB, no fibrosis) were assigned to oat bran (4.5 g oat β-glucan, total fiber 11.7 g/day), spelt bran (11.7 g fiber/day), or placebo (2.1 g fiber/day) for 12 weeks. During the Run-in phase, dietary assessment alone significantly decreased BMI and liver enzymes (ALT, AST, γ-GT) while increasing microbiota diversity. Improvements were maintained in all three intervention groups. However, no significant changes were observed in hepatic steatosis (CAP), overall microbiota composition, and serum bile acid profiles. Dietary assessment alone improved MASLD biomarkers, with the fiber supplementation offering no additional benefit. This highlights the importance of dietary counseling in MASLD management. (clinical trials: NCT03897218).

Alejandro Belanche, André Bannink, Jan Dijkstra et al.

ABSTRACT: This publication aims to provide guidelines of the knowledge required and the potential research to be conducted in order to understand the mode of action of antimethanogenic feed additives (AMFA). In the first part of the paper, we classify AMFA into 4 categories according to their mode of action: (1) lowering dihydrogen (H2) production; (2) inhibiting methanogens; (3) promoting alternative H2-incorporating pathways; and (4) oxidizing methane (CH4). The second part of the paper presents questions that guide the research to identify the mode of action of an AMFA on the rumen CH4 production from 5 different perspectives: (1) microbiology; (2) cell and molecular biochemistry; (3) microbial ecology; (4) animal metabolism; and (5) cross-cutting aspects. Recommendations are provided to address various research questions within each perspective, along with examples of how aspects of the mode of action of AMFA have been elucidated before. In summary, this paper offers timely and comprehensive guidelines to better understand and reveal the mode of action of current and emerging AMFA.

Doudou Ge, Chongwen Yin, Jiayu Jing et al.

The evolution of phytophagous insects has resulted in the development of feeding specializations that are unique to this group. The majority of current research on insect palatability has concentrated on aspects of ecology and biology, with relatively little attention paid to the role of insect gut symbiotic bacteria. Symbiont bacteria have a close relationship with their insect hosts and perform a range of functions. This research aimed to investigate the relationship between insect host plant range and gut symbiotic bacteria. A synthesis of the extant literature on the intestinal commensal bacteria of monophagous, oligophagous, and polyphagous tephritids revealed no evidence of a positive correlation between the plant host range and the diversity of larval intestinal microbial species. The gut symbionts of same species were observed to exhibit discrepancies between different literature sources, which were attributed to variations in multiple environmental factors. However, following beta diversity analysis, monophagy demonstrated the lowest level of variation in intestinal commensal bacteria, while polyphagous tephritids exhibited the greatest variation in intestinal commensal bacteria community variation. In light of these findings, this study proposes the hypothesis that exclusive or closely related plant hosts provide monophagy and oligophagy with a stable core colony over long evolutionary periods. The core flora is closely associated with host adaptations in monophagous and oligophagous tephritids, including nutritional and detoxification functions. This is in contrast to polyphagy, whose dominant colony varies in different environments. Our hypothesis requires further refinement of the data on the gut commensal bacteria of monophagy and oligophagy as the number of species and samples is currently limited.

Ngonidzashe Mangoma, Nerve Zhou, Thembekile Ncube

The use of metagenomics has substantially improved our understanding of the taxonomy, phylogeny and ecology of extreme environment microbiomes. Advances in bioinformatics now permit the reconstruction of almost intact microbial genomes, called metagenome-assembled genomes (MAGs), from metagenomic sequence data, allowing for more precise cell-level taxonomic, phylogenetic and functional profiling of uncultured extremophiles. Here, we report on the recovery and characterisation of metagenome-assembled genomes from the Buhera soda pans located in eastern Zimbabwe. This ecosystem has not been studied despite its unique geochemistry and potential as a habitat for unique microorganisms. Metagenomic DNA from the soda pan was sequenced using the DNA Nanoball Sequencing (DNBSEQR) technique. Sequence analysis, done on the Knowledgebase (KBase) platform, involved quality assessment, read assembly, contig binning, and MAG extraction. The MAGs were subjected to taxonomic placement, phylogenetic profiling and functional annotation in order to establish their possible ecological roles in the soda pan ecosystem. A total of 16 bacterial MAGs of medium to high quality were recovered, all distributed among five phyla dominated by Pseudomonadota and Bacillota. Of the ten MAGs that were taxonomically classified up to genus level, five of them belonged to the halophilic/ haloalkaliphilic genera Alkalibacterium, Vibrio, Thioalkalivibrio, Cecembia and Nitrincola, underscoring the importance of haloalkaliphiles in the Buhera soda pans. Functional profiling revealed the possession of diverse carbohydrate-metabolising pathways by the MAGs, with glycolysis and the pentose phosphate pathways appearing to be key pathways in this ecosystem. Several MAGs possessed pathways that implicated them in some key aspects of the nitrogen and sulphur cycle. Some MAGs harboured both sulphate reduction and respiratory pathways, suggesting a possible mechanism of ATP biosynthesis through sulphate respiration. This study demonstrates the feasibility of the recovery and taxonomic and functional annotation of high quality microbial genomes from extreme environments, making it possible to establish the ecological roles and biotechnological potential of uncultured microorganisms.

Haowen Qiu, Rees Checketts, Mariah Kay Jackson et al.

Chronic Obstructive Pulmonary Disease (COPD) affects 30 million Americans. Previous epidemiologic work has shown that diet can impact pulmonary function in those with and without COPD. Diet is also a major driver of gut microbiome composition and function. Importantly, the gut microbiome has also been associated with lung health (i.e., the gut-lung axis) in both preclinical and clinical studies. Despite this growing body of evidence, many questions remain regarding the gut-lung axis. Specifically, how the microbiome impacts the relationship between diet factors and spirometry or stage of disease in people with COPD is little understood. We hypothesize that there are taxonomic differences in the gut microbiome among the different stages of COPD and that diet microbiome interactions influence pulmonary function. This study aimed to identify how the GI microbiota correlated with the severity of respiratory disease in COPD patients and how the microbiome may mediate the relationship between diet, including fiber and omega-3 fatty acids, and lung function outcomes.

Qingmei Liu, Chuhao Li, Xiaohan Zhang et al.

ABSTRACT As one of the most notorious and successful phytopathogenic bacteria, Ralstonia solanacearum controls the transition between long-term survival and pathogenic modes through an intricate regulatory network, the understanding of which remains incomplete despite years of effort. In this study, we identified PhcX, a previously uncharacterized response regulator in R. solanacearum, and uncovered its essential functions in modulating virulence and metabolism. The phcX deletion mutant exhibited substantial phenotypic alterations, including slower initial growth, altered response to host extract, reduced motilities, polygalacturonase activity, and exopolysaccharide production, elevated biofilm formation, delayed hypersensitive response, and impaired virulence. Moreover, ~16% of all genes were differentially expressed in the mutant, among which the genes associated with virulence, nitrogen metabolism, and regulation were overrepresented (e.g., most T3SS/T3Es genes). Many of these traits and genes were regulated by PhcX and the global virulence regulator PhcA, but 81.4% of the genes were regulated in opposite directions. The functions of PhcX were largely conserved in R. solanacearum EP1 and GMI1000 strains. Apparent orthologs of PhcX are widely distributed in Proteobacteria, including the LqsR quorum sensing (QS) response regulator in Legionella pneumophilia. Notably, our data suggest that phcX was originally part of the Lqs QS system but was decoupled from Lqs in Ralstonia/Cupriavidus, physically linked to the phc QS genes, and connected with the virulence regulatory network in Ralstonia during its evolution. The findings of this study contribute to a better understanding of the virulence and metabolism regulation mechanisms in R. solanacearum and shed light on the evolution of its complex regulatory network. IMPORTANCE The bacterial wilt caused by the soil-borne phytopathogen Ralstonia solanacearum is one of the most destructive crop diseases. To achieve a successful infection, R. solanacearum has evolved an intricate regulatory network to orchestrate the expression of an arsenal of virulence factors and fine-tune the allocation of energy. However, despite the wealth of knowledge gained in the past decades, many players and connections are still missing from the network. The importance of our study lies in the identification of PhcX, a novel conserved global regulator with critical roles in modulating the virulence and metabolism of R. solanacearum. PhcX affects many well-characterized regulators and exhibits contrasting modes of regulation from the central regulator PhcA on a variety of virulence-associated traits and genes. Our findings add a valuable piece to the puzzle of how the pathogen regulates its proliferation and infection, which is critical for understanding its pathogenesis and developing disease control strategies.

Stefan Thiele, Julia E. Storesund, Mar Fernández-Méndez et al.

The Arctic is warming 2–3 times faster than the global average, leading to a decrease in Arctic sea ice extent, thickness, and associated changes in sea ice structure. These changes impact sea ice habitat properties and the ice-associated ecosystems. Sea-ice algal blooms provide various algal-derived carbon sources for the bacterial and archaeal communities within the sea ice. Here, we detail the transition of these communities from winter through spring to early summer during the Norwegian young sea ICE (N-ICE2015) expedition. The winter community was dominated by the archaeon <i>Candidatus</i> Nitrosopumilus and bacteria belonging to the <i>Gammaproteobacteria</i> (<i>Colwellia</i>, <i>Kangiellaceae,</i> and <i>Nitrinocolaceae</i>), indicating that nitrogen-based metabolisms, particularly ammonia oxidation to nitrite by <i>Cand.</i> Nitrosopumilus was prevalent. At the onset of the vernal sea-ice algae bloom, the community shifted to the dominance of <i>Gammaproteobacteria</i> (<i>Kangiellaceae, Nitrinocolaceae</i>) and <i>Bacteroidia</i> (<i>Polaribacter</i>), while <i>Cand.</i> Nitrosopumilus almost disappeared. The bioinformatically predicted carbohydrate-active enzymes increased during spring and summer, indicating that sea-ice algae-derived carbon sources are a strong driver of bacterial and archaeal community succession in Arctic sea ice during the change of seasons. This implies a succession from a nitrogen metabolism-based winter community to an algal-derived carbon metabolism-based spring/ summer community.

Jin-tian Li, Pu Jia, Xiao-juan Wang et al.

Abstract The widespread occurrence of sulfate-reducing microorganisms (SRMs) in temporarily oxic/hypoxic aquatic environments indicates an intriguing possibility that SRMs can prevail in constantly oxic/hypoxic terrestrial sulfate-rich environments. However, little attention has been given to this possibility, leading to an incomplete understanding of microorganisms driving the terrestrial part of the global sulfur (S) cycle. In this study, genome-centric metagenomics and metatranscriptomics were employed to explore the diversity, metabolic potential, and gene expression profile of SRMs in a revegetated acidic mine wasteland under constantly oxic/hypoxic conditions. We recovered 16 medium- to high-quality metagenome-assembled genomes (MAGs) containing reductive dsrAB. Among them, 12 and four MAGs belonged to Acidobacteria and Deltaproteobacteria, respectively, harboring three new SRM genera. Comparative genomic analysis based on seven high-quality MAGs (completeness >90% and contamination <10%; including six acidobacterial and one deltaproteobacterial) and genomes of three additional cultured model species showed that Acidobacteria-related SRMs had more genes encoding glycoside hydrolases, oxygen-tolerant hydrogenases, and cytochrome c oxidases than Deltaproteobacteria-related SRMs. The opposite pattern was observed for genes encoding superoxide reductases and thioredoxin peroxidases. Using VirSorter, viral genome sequences were found in five of the 16 MAGs and in all three cultured model species. These prophages encoded enzymes involved in glycoside hydrolysis and antioxidation in their hosts. Moreover, metatranscriptomic analysis revealed that 15 of the 16 SRMs reported here were active in situ. An acidobacterial MAG containing a prophage dominated the SRM transcripts, expressing a large number of genes involved in its response to oxidative stress and competition for organic matter.

Kazumori Mise, Wataru Iwasaki

Abstract Metagenome-assembled genomes (MAGs) have revealed the hidden diversity and functions of uncultivated microbes, but their reconstruction from metagenomes remains a computationally difficult task. Repetitive or exogenous sequences, such as ribosomal RNA and horizontally transferred genes, are frequently absent from MAGs because of misassembly and binning errors. Here, we report that ribosomal protein genes are also often absent from MAGs, although they are neither repetitive nor exogenous. Comprehensive analyses of more than 190,000 MAGs revealed that these genes could be missing in more than 20–40% of near-complete (i.e., with completeness of 90% or higher) MAGs. While some uncultivated environmental microbes intrinsically lack some ribosomal protein genes, we found that this unexpected absence is largely due to special evolutionary patterns of codon usage bias in ribosomal protein genes and algorithmic characteristics of metagenomic binning, which is dependent on tetranucleotide frequencies of contigs. This problem reflects the microbial life-history strategy. Fast-growing microbes tend to have this difficulty, likely because of strong evolutionary pressures on ribosomal protein genes toward the efficient assembly of ribosomes. Our observations caution those who study genomics and phylogeny of uncultivated microbes, the diversity and evolution of microbial genes in the central dogma, and bioinformatics in metagenomics.

Ana Larroya, Jorge Pantoja, Jorge Pantoja et al.

Mental health is determined by a complex interplay between the Neurological Exposome and the Human Genome. Multiple genetic and non-genetic (exposome) factors interact early in life, modulating the risk of developing the most common complex neurodevelopmental disorders (NDDs), with potential long-term consequences on health. To date, the understating of the precise etiology underpinning these neurological alterations, and their clinical management pose a challenge. The crucial role played by diet and gut microbiota in brain development and functioning would indicate that modulating the gut-brain axis may help protect against the onset and progression of mental-health disorders. Some nutritional deficiencies and gut microbiota alterations have been linked to NDDs, suggesting their potential pathogenic implications. In addition, certain dietary interventions have emerged as promising alternatives or adjuvant strategies for improving the management of particular NDDs, at least in particular subsets of subjects. The gut microbiota can be a key to mediating the effects of other exposome factors such as diet on mental health, and ongoing research in Psychiatry and Neuropediatrics is developing Precision Nutrition Models to classify subjects according to a diet response prediction based on specific individual features, including microbiome signatures. Here, we review current scientific evidence for the impact of early life environmental factors, including diet, on gut microbiota and neuro-development, emphasizing the potential long-term consequences on health; and also summarize the state of the art regarding the mechanisms underlying diet and gut microbiota influence on the brain–gut axis. Furthermore, we describe the evidence supporting the key role played by gut microbiota, diet and nutrition in neurodevelopment, as well as the effectiveness of certain dietary and microbiome-based interventions aimed at preventing or treating NDDs. Finally, we emphasize the need for further research to gain greater insight into the complex interplay between diet, gut microbiome and brain development. Such knowledge would help towards achieving tailored integrative treatments, including personalized nutrition.

Jamie N. Orr, Jamie N. Orr, Roy Neilson et al.

Pasteuria spp. are endospore forming bacteria which act as natural antagonists to many of the most economically significant plant parasitic nematodes (PPNs). Highly species-specific nematode suppression may be observed in soils containing a sufficiently high density of Pasteuria spp. spores. This suppression is enacted by the bacteria via inhibition of root invasion and sterilization of the nematode host. Molecular methods for the detection of Pasteuria spp. from environmental DNA (eDNA) have been described; however, these methods are limited in both scale and in depth. We report the use of small subunit rRNA gene metabarcoding to profile Pasteuria spp. and nematode communities in parallel. We have investigated Pasteuria spp. population structure in Scottish soils using eDNA from two sources: soil extracted DNA from the second National Soil Inventory of Scotland (NSIS2); and nematode extracted DNA collected from farms in the East Scotland Farm Network (ESFN). We compared the Pasteuria spp. community culture to both nematode community structure and the physiochemical properties of soils. Our results indicate that Pasteuria spp. populations in Scottish soils are broadly dominated by two sequence variants. The first of these aligns with high identity to Pasteuria hartismeri, a species first described parasitizing Meloidogyne ardenensis, a nematode parasite of woody and perennial plants in northern Europe. The second aligns with a Pasteuria-like sequence which was first recovered from a farm near Edinburgh which was found to contain bacterial feeding nematodes and Pratylenchus spp. encumbered by Pasteuria spp. endospores. Further, soil carbon, moisture, bulk density, and pH showed a strong correlation with the Pasteuria spp. community composition. These results indicate that metabarcoding is appropriate for the sensitive, specific, and semi-quantitative profiling of Pasteuria species from eDNA.

Perrine Cruaud, Perrine Cruaud, Perrine Cruaud et al.

Protists are key stone components of aquatic ecosystems, sustaining primary productivity and aquatic food webs. However, their diversity, ecology and structuring factors shaping their temporal distribution remain strongly misunderstood in freshwaters. Using high-throughput sequencing on water samples collected over 16 different months (including two summer and two winter periods), combined with geochemical measurements and climate monitoring, we comprehensively determined the pico- and nanoeukaryotic community composition and dynamics in a Canadian river undergoing prolonged ice-cover winters. Our analysis revealed a large protist diversity in this fluctuating ecosystem and clear seasonal patterns demonstrating a direct and/or indirect selective role of abiotic factors, such as water temperature or nitrogen concentrations, in structuring the eukaryotic microbial community. Nonetheless, our results also revealed that primary productivity, predatory as well as parasitism lifestyles, inferred from fine phylogenetic placements, remained potentially present over the annual cycle, despite the large seasonal fluctuations and the remodeling of the community composition under ice. In addition, potential interplays with the bacterial community composition were identified supporting a possible contribution of the bacterial community to the temporal dynamics of the protist community structure. Our results illustrate the complexity of the eukaryotic microbial community and provide a substantive and useful dataset to better understand the global freshwater ecosystem functioning.

Lesley Hoyles, Maria L. Jiménez-Pranteda, Julien Chilloux et al.

Abstract Background The dietary methylamines choline, carnitine, and phosphatidylcholine are used by the gut microbiota to produce a range of metabolites, including trimethylamine (TMA). However, little is known about the use of trimethylamine N-oxide (TMAO) by this consortium of microbes. Results A feeding study using deuterated TMAO in C57BL6/J mice demonstrated microbial conversion of TMAO to TMA, with uptake of TMA into the bloodstream and its conversion to TMAO. Microbial activity necessary to convert TMAO to TMA was suppressed in antibiotic-treated mice, with deuterated TMAO being taken up directly into the bloodstream. In batch-culture fermentation systems inoculated with human faeces, growth of Enterobacteriaceae was stimulated in the presence of TMAO. Human-derived faecal and caecal bacteria (n = 66 isolates) were screened on solid and liquid media for their ability to use TMAO, with metabolites in spent media analysed by 1H-NMR. As with the in vitro fermentation experiments, TMAO stimulated the growth of Enterobacteriaceae; these bacteria produced most TMA from TMAO. Caecal/small intestinal isolates of Escherichia coli produced more TMA from TMAO than their faecal counterparts. Lactic acid bacteria produced increased amounts of lactate when grown in the presence of TMAO but did not produce large amounts of TMA. Clostridia (sensu stricto), bifidobacteria, and coriobacteria were significantly correlated with TMA production in the mixed fermentation system but did not produce notable quantities of TMA from TMAO in pure culture. Conclusions Reduction of TMAO by the gut microbiota (predominantly Enterobacteriaceae) to TMA followed by host uptake of TMA into the bloodstream from the intestine and its conversion back to TMAO by host hepatic enzymes is an example of metabolic retroconversion. TMAO influences microbial metabolism depending on isolation source and taxon of gut bacterium. Correlation of metabolomic and abundance data from mixed microbiota fermentation systems did not give a true picture of which members of the gut microbiota were responsible for converting TMAO to TMA; only by supplementing the study with pure culture work and additional metabolomics was it possible to increase our understanding of TMAO bioconversions by the human gut microbiota.

Marius Bredon, Jessica Dittmer, Cyril Noël et al.

Abstract Background Woodlice are recognized as keystone species in terrestrial ecosystems due to their role in the decomposition of organic matter. Thus, they contribute to lignocellulose degradation and nutrient cycling in the environment together with other macroarthropods. Lignocellulose is the main component of plants and is composed of cellulose, lignin and hemicellulose. Its digestion requires the action of multiple Carbohydrate-Active enZymes (called CAZymes), typically acting together as a cocktail with complementary, synergistic activities and modes of action. Some invertebrates express a few endogenous lignocellulose-degrading enzymes but in most species, an efficient degradation and digestion of lignocellulose can only be achieved through mutualistic associations with endosymbionts. Similar to termites, it has been suspected that several bacterial symbionts may be involved in lignocellulose degradation in terrestrial isopods, by completing the CAZyme repertoire of their hosts. Results To test this hypothesis, host transcriptomic and microbiome shotgun metagenomic datasets were obtained and investigated from the pill bug Armadillidium vulgare. Many genes of bacterial and archaeal origin coding for CAZymes were identified in the metagenomes of several host tissues and the gut content of specimens from both laboratory lineages and a natural population of A. vulgare. Some of them may be involved in the degradation of cellulose, hemicellulose, and lignin. Reconstructing a lignocellulose-degrading microbial community based on the prokaryotic taxa contributing relevant CAZymes revealed two taxonomically distinct but functionally redundant microbial communities depending on host origin. In parallel, endogenous CAZymes were identified from the transcriptome of the host and their expression in digestive tissues was demonstrated by RT-qPCR, demonstrating a complementary enzyme repertoire for lignocellulose degradation from both the host and the microbiome in A. vulgare. Conclusions Our results provide new insights into the role of the microbiome in the evolution of terrestrial isopods and their adaptive radiation in terrestrial habitats.

Abdel-Azeem AM

Divakara ST, Aiyaz M,, Chandra Nayaka S et al.

The Aspergillus flavus and aflatoxins are known to be detrimental to plant and animals<br />affecting their productivity and yield. This study evaluated effects of toxigenic A. flavus and<br />aflatoxins on physical parameters like seed germination, seedling vigor, root length, shoot length<br />and also biochemical parameters like chlorophyll content, protein, sugars and amylase activity in<br />sorghum seeds. The sorghum seeds were treated with 100, 250 and 500 μg ml-1 concentrations of<br />aflatoxins and likewise, A. flavus spore suspension adjusted to 1x108 spores ml-1 were also<br />treated to seeds in different treatments. The experimental results revealed maximum inhibition of<br />seed germination, seedling vigor, chlorophyll, proteins, total sugars and α-amylase activity in the<br />sorghum seedlings was observed at 500 μg ml-1 followed by 250 and 100 μg ml-1. But seed<br />treatment with toxigenic A. flavus spore suspension showed slight inhibition all the above<br />parameters tested when compared to untreated control, but there was no significant decrease was<br />observed. The study highlighted negative effects of the A. flavus and aflatoxins on the tested seed<br />quality parameters tested there by necessitating need of monitoring of toxigenic fungi and their<br />metabolites in sorghum seeds.

Michael eKühl, Michael eKühl, Michael eKühl et al.

The discovery of the cyanobacterium Prochloron was the first finding of a bacterial oxyphototroph with chlorophyll (Chl) b, in addition to Chl a. It was first described as Prochloron didemni but a number of clades have since been described. Prochloron is a conspicuously large (7-25 &#181;m) unicellular cyanobacterium living in a symbiotic relationship, primarily with (sub-) tropical didemnid ascidians; it has resisted numerous cultivation attempts and appears truly obligatory symbiotic. Recently, a Prochloron draft genome was published, revealing no lack of metabolic genes that could explain the apparent inability to reproduce and sustain photosynthesis in a free-living stage. Possibly, the unsuccessful cultivation is partly due to a lack of knowledge about the microenvironmental conditions and ecophysiology of Prochloron in its natural habitat. We used microsensors, variable chlorophyll fluorescence imaging and imaging of O2 and pH to obtain a detailed insight to the microenvironmental ecology and photobiology of Prochloron in hospite in the didemnid ascidian Lissoclinum patella. The microenvironment within ascidians is characterized by steep gradients of light and chemical parameters that change rapidly with varying irradiances. The interior zone of the ascidians harboring Prochloron thus became anoxic and acidic within a few min of darkness, while the same zone exhibited O2 super-saturation and strongly alkaline pH after a few min of illumination. Photosynthesis showed lack of photoinhibition even at high irradiances equivalent to full sunlight, and photosynthesis recovered rapidly after periods of anoxia. We discuss these new insights on the ecological niche of Prochloron and possible interactions with its host and other microbes in light of its recently published genome and a recent study of the overall microbial diversity and metagenome of L. patella.