Aetiology: Koch's postulates fulfilled for SARS virus.
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ABSTRACT:
SUBMITTER: Fouchier RA
PROVIDER: S-EPMC7095368 | biostudies-literature | 2003 May
REPOSITORIES: biostudies-literature
Publications
Aetiology: Koch's postulates fulfilled for SARS virus.
Fouchier Ron A M RA Kuiken Thijs T Schutten Martin M van Amerongen Geert G van Doornum Gerard J J GJ van den Hoogen Bernadette G BG Peiris Malik M Lim Wilina W Stöhr Klaus K Osterhaus Albert D M E AD
Nature 20030501 6937
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Project description:BackgroundRecently, increasing evidence supports that some complex diseases are not attributed to a given pathogen, but dysbiosis in the host intestinal microbiota (IM). The full intestinal ecosystem alterations, rather than a single pathogen, are associated with white feces syndrome (WFS), a globally severe non-infectious shrimp disease, while no experimental evidence to explore the causality. Herein, we conducted comprehensive metagenomic and metabolomic analysis, and intestinal microbiota transplantation (IMT) to investigate the causal relationship between IM dysbiosis and WFS.ResultsCompared to the Control shrimp, we found dramatically decreased microbial richness and diversity in WFS shrimp. Ten genera, such as Vibrio, Candidatus Bacilloplasma, Photobacterium, and Aeromonas, were overrepresented in WFS, whereas 11 genera, including Shewanella, Chitinibacter, and Rhodobacter were enriched in control. The divergent changes in these populations might contribute the observation that a decline of pathways conferring lipoic acid metabolism and mineral absorption in WFS. Meanwhile, some sorts of metabolites, especially lipids and organic acids, were found to be related to the IM alteration in WFS. Integrated with multiomics and IMT, we demonstrated that significant alterations in the community composition, functional potentials, and metabolites of IM were closely linked to shrimp WFS. The distinguished metabolites which were attributed to the IM dysbiosis were validated by feed-supplementary challenge. Both homogenous selection and heterogeneous selection process were less pronounced in WFS microbial community assembly. Notably, IMT shrimp from WFS donors eventually developed WFS clinical signs, while the dysbiotic IM can be recharacterized in recipient shrimp.ConclusionsCollectively, our findings offer solid evidence of the causality between IM dysbiosis and shrimp WFS, which exemplify the 'microecological Koch's postulates' (an intestinal microbiota dysbiosis, a disease) in disease etiology, and inspire our cogitation on etiology from an ecological perspective. Video abstract.
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Project description:Candidatus Liberibacter asiaticus (Las) is one of the causal agents of huanglongbing (HLB), the most devastating disease of citrus worldwide. Due to the intracellular lifestyle and significant genome reduction, culturing Las in vitro has proven to be extremely challenging. In this study, we optimized growth conditions and developed a semi-selective medium based on the results of nutritional and antibiotic screening assays. Using these optimized conditions, we were able to grow Las in the LG liquid medium with ca.100- to 1000-fold increase, which peaked after 4 to 6 weeks and were estimated to contain 106 to 107 cells/ml. The cultured Las bacteria remained in a dynamic state of growth for over 20 months and displayed limited growth in subcultures. The survival and growth of Las was confirmed by fluorescence in situ hybridization with Las-specific probes and expression of its metabolic genes. Growth of Las in the optimized medium relied on the presence of a helper bacterium, Stenotrophomonas maltophilia FLMAT-1 that is multi-drug resistant and dominant in the Las co-culture system. To recapitulate the disease, the co-cultured Las was inoculated back to citrus seedlings via psyllid feeding. Although the Las-positive rate of the fed psyllids and inoculated plants were relatively low, this is the first demonstration of partial fulfillment of Koch's postulates with significant growth of Las in vitro and a successful inoculation of cultured Las back to psyllids and citrus plants that resulted in HLB symptoms. These results provide new insights into Las growth in vitro and a system for improvement towards axenic culture and anti-Las compound screening.
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Project description:Early establishment of endophytes can play a role in pathogen suppression and improve seedling development. One route for establishment of endophytes in seedlings is transmission of bacteria from the parent plant to the seedling via the seed. In wheat seeds, it is not clear whether this transmission route exists, and the identities and location of bacteria within wheat seeds are unknown. We identified bacteria in the wheat (Triticum aestivum) cv. Hereward seed environment using embryo excision to determine the location of the bacterial load. Axenic wheat seedlings obtained with this method were subsequently used to screen a putative endophyte bacterial isolate library for endophytic competency. This absence of bacteria recovered from seeds indicated low bacterial abundance and/or the presence of inhibitors. Diversity of readily culturable bacteria in seeds was low with 8 genera identified, dominated by Erwinia and Paenibacillus. We propose that anatomical restrictions in wheat limit embryo associated vertical transmission, and that bacterial load is carried in the seed coat, crease tissue and endosperm. This finding facilitates the creation of axenic wheat plants to test competency of putative endophytes and also provides a platform for endophyte competition, plant growth, and gene expression studies without an indigenous bacterial background.
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Project description:BackgroundFor more than a century, the Koch's postulates have been the golden rule for determining the causative agents in diseases. However, in cases of multiple pathogens-one disease, in which different pathogens can cause the same disease, the selection of microorganisms that regress infection is hard when Koch's postulates are applied. Microbiome approaches can obtain relatively complete information about disease-related microorganisms and can guide the selection of target microorganisms for regression infection. In the present study, whitish muscle syndrome (WMS) of Scylla paramamosain, which has typical symptoms with whitish muscle and blackened hemolymph was used as an example to establish a new research strategy that integrates microbiome approaches and Koch's postulates to determinate causative agents of multiple pathogens-one disease.ResultsMicrobiome results revealed that Aeromonas, Acinetobacter, Shewanella, Chryseomicrobium, Exiguobacterium, Vibrio and Flavobacterium, and Kurtzmaniella in hemolymph were bacterial and fungal indicators for WMS. A total of 23 bacteria and 14 fungi were isolated from hemolymph and muscle tissues, and among the bacteria, Shewanella chilikensis, S. xiamenensis, Vibrio alginolyticus, S. putrefaciens, V. fluvialis, and V. parahaemolyticus were present in hemolymph and/or muscle tissues in each WMS crab, and the last three species were also present in three Healthy crabs. The target bacteria and fungi were further screened to regression infections based on two criteria: whether they belonged to the indicator genera for WMS, whether they were isolated from both hemolymph and muscle tissues in most WMS crabs. Only S. chilikensis, S. putrefaciens, S. xiamenensis, V. alginolyticus, V. fluvialis, and V. parahaemolyticus met both two criteria. The six bacteria that met both two criteria and six fungi and another bacterium that unmatched any of two criteria were used to perform regression infection experiments based on Koch's postulates. S. chilikensis, S. putrefaciens, S. xiamenensis, V. alginolyticus, V. fluvialis, and V. parahaemolyticus met both two criteria, and the results indicate that they cause WMS in crabs independently.ConclusionsThis study fully demonstrated that our research strategy that integrates the microbiome and Koch's postulates can maximize the ability to catch pathogens in one net for the situation of multiple pathogens-one disease. Video Abstract.
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