ORCID Profile
0000-0002-4975-2946
Current Organisation
University of Vienna
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Publisher: Wiley
Date: 25-08-2010
DOI: 10.1111/J.1365-2958.2010.07286.X
Abstract: Vibrio2009, the third international conference on the biology of Vibrios, was held in Rio de Janeiro, Brazil, in November 2009. This conference united researchers studying various aspects of pathogenesis, symbiosis and environmental persistence of this erse group of marine bacteria. Through many of the presentations, it became apparent how horizontal gene transfer and genetic flexibility has driven the incredible ersity of these microbes. Interestingly, unifying themes of behaviour could be seen in the interaction(s) of Vibrios with other organisms, such as with other bacteria, corals, invertebrates and humans. Presentations illuminated the idea that the path towards symbiosis is not that different from the path towards disease, and that alterations in environmental conditions, such as climate change, can tip the balance and change the Vibrio interactions from benign to pathogenic.
Publisher: Proceedings of the National Academy of Sciences
Date: 18-03-2008
Abstract: Because ocean water is typically resource-poor, bacteria may gain significant growth advantages if they can exploit the ephemeral nutrient patches originating from numerous, small sources. Although this interaction has been proposed to enhance biogeochemical transformation rates in the ocean, it remains questionable whether bacteria are able to efficiently use patches before physical mechanisms dissipate them. Here we show that the rapid chemotactic response of the marine bacterium Pseudoalteromonas haloplanktis substantially enhances its ability to exploit nutrient patches before they dissipate. We investigated two types of patches important in the ocean: nutrient pulses and nutrient plumes, generated for ex le from lysed algae and sinking organic particles, respectively. We used microfluidic devices to create patches with environmentally realistic dimensions and dynamics. The accumulation of P. haloplanktis in response to a nutrient pulse led to formation of bacterial hot spots within tens of seconds, resulting in a 10-fold higher nutrient exposure for the fastest 20% of the population compared with nonmotile cells. Moreover, the chemotactic response of P. haloplanktis was times faster than the classic chemotaxis model Escherichia coli , leading to twice the nutrient exposure. We demonstrate that such rapid response allows P. haloplanktis to colonize nutrient plumes for realistic particle sinking speeds, with up to a 4-fold nutrient exposure compared with nonmotile cells. These results suggest that chemotactic swimming strategies of marine bacteria in patchy nutrient seascapes exert strong influence on carbon turnover rates by triggering the formation of microscale hot spots of bacterial productivity.
Publisher: Microbiology Society
Date: 09-2014
Abstract: A Gram-staining-negative, curved-rod-shaped bacterium with close resemblance to Vibrio cholerae , the aetiological agent of cholera, was isolated over the course of several years from coastal brackish water (17 strains) and from clinical cases (two strains) in the United States. 16S rRNA gene identity with V. cholerae exceeded 98 % yet an average nucleotide identity based on genome data of around 86 % and multi locus sequence analysis of six housekeeping genes ( mdh , adk , gyrB , recA, pgi and rpoB ) clearly delineated these isolates as a distinct genotypic cluster within the V. cholerae – V. mimicus clade. Most standard identification techniques do not differentiate this cluster of isolates from V. cholerae . Only lification of the ompW gene using V. cholerae -specific primers and a negative Voges–Proskauer test showed a difference between the two clusters. Additionally, all isolated strains differed phenotypically from V. cholerae in their ability to utilize N -acetyl- d -galactosamine and d -glucuronic acid as sole carbon sources. Furthermore, they were generally unable to infect the slime mould Dictyostelium discoideum , a widespread ability in V. cholerae . Based on these clear phenotypic differences that are not necessarily apparent in standard tests as well as average nucleotide identity and phylogeny of protein-coding genes, we propose the existence of a novel species, Vibrio metoecus sp. nov. with the type strain OP3H T ( = LMG 27764 T = CIP 110643 T ). Due to its close resemblance to V. cholerae and the increasing number of strains isolated over the past several years, we suggest that V. metoecus sp. nov. is a relatively common species of the genus Vibrio , isolates of which have been identified as atypical isolates of V. cholerae in the past. Its isolation from clinical s les also indicates that strains of this species, like V. cholerae , are opportunistic pathogens.
Publisher: Wiley
Date: 09-2010
DOI: 10.1111/J.1462-2920.2010.02328.X
Abstract: Although animal-associated microbial communities (microbiomes) are increasingly recognized to influence health, the extent to which animals represent highly selective habitats for microbes leading to predominance of high host specificity remains poorly understood. Here, we show that vibrios, which are well-known commensals and opportunistic pathogens of marine animals, overall display little host preference, likely because of efficient dispersal-colonization dynamics mediated by food items. We isolated 1753 strains from water and animal s les, which are linked in a food chain and display different degrees of similarity (respiratory and digestive tract of mussels and crabs, live and dead zooplankton, and whole water s les). Multilocus sequence data served as input for modelling and statistical analysis of spatiotemporal population structure. These data showed that the majority of populations occurred broadly within and among hosts, with the dominant population being a near perfect generalist with regard to seasons, host taxa and body regions. Zooplankton harboured the fewest and most specific populations, while crabs and mussels contained the highest ersity with little evidence for host preferences. Most mussel- and crab-associated populations were detected in water s les at similar frequencies, particularly in filter-feeding mussels where populations were also evenly distributed across host in iduals. The higher variation among in iduals observed in crabs and zooplankton is consistent with stochastic clonal expansions. These patterns suggest that evolution of a high degree of host specificity is surprisingly rare even though these animals represent long-lived habitats, and vibrios are consistent members of their microbiome. Instead, many of the populations show stronger association with planktonic (micro)habitats while the microbiome may be a fairly open system for vibrios in which high rates of immigration can outpace selection for specialization.
Publisher: American Society for Microbiology
Date: 29-04-2011
Abstract: Vibrio cholerae represents both an environmental pathogen and a widely distributed microbial species comprised of closely related strains occurring in the tropical to temperate coastal ocean across the globe (Colwell RR, Science 274:2025–2031, 1996 Griffith DC, Kelly-Hope LA, Miller MA, Am. J. Trop. Med. Hyg. 75:973–977, 2006 Reidl J, Klose KE, FEMS Microbiol. Rev. 26:125–139, 2002). However, although this implies dispersal and growth across erse environmental conditions, how locally successful populations assemble from a possibly global gene pool, relatively unhindered by geographic boundaries, remains poorly understood. Here, we show that environmental Vibrio cholerae possesses two, largely distinct gene pools: one is vertically inherited and globally well mixed, and the other is local and rapidly transferred across species boundaries to generate an endemic population structure. While phylogeographic analysis of isolates collected from Bangladesh and the U.S. east coast suggested strong panmixis for protein-coding genes, there was geographic structure in integrons, which are the only genomic islands present in all strains of V. cholerae (Chun J, et al., Proc. Natl. Acad. Sci. U. S. A. 106:15442–15447, 2009) and are capable of acquiring and expressing mobile gene cassettes. Geographic differentiation in integrons arises from high gene turnover, with acquisition from a locally cooccurring sister species being up to twice as likely as exchange with conspecific but geographically distant V. cholerae populations. IMPORTANCE Functional predictions of integron genes show the predominance of secondary metabolism and cell surface modification, which is consistent with a role in competition and predation defense. We suggest that the integron gene pool’s distinctness and tempo of sharing are adaptive in allowing rapid conversion of genomes to reflect local ecological constraints. Because the integron is frequently the main element differentiating clinical strains (Chun J, et al., Proc. Natl. Acad. Sci. U. S. A. 106:15442–15447, 2009) and its recombinogenic activity is directly stimulated by environmental stresses (Guerin E, et al., Science 324:1034, 2009), these observations are relevant for local emergence and subsequent dispersal.
Publisher: Springer Science and Business Media LLC
Date: 23-12-2014
DOI: 10.1007/S00203-014-1071-2
Abstract: Microbial taxonomy should provide adequate descriptions of bacterial, archaeal, and eukaryotic microbial ersity in ecological, clinical, and industrial environments. Its cornerstone, the prokaryote species has been re-evaluated twice. It is time to revisit polyphasic taxonomy, its principles, and its practice, including its underlying pragmatic species concept. Ultimately, we will be able to realize an old dream of our predecessor taxonomists and build a genomic-based microbial taxonomy, using standardized and automated curation of high-quality complete genome sequences as the new gold standard.
Publisher: American Society for Microbiology
Date: 15-09-2016
DOI: 10.1128/AEM.01177-16
Abstract: Vibrio cholerae is a ubiquitous aquatic microbe in temperate and tropical coastal areas. It is a erse species, with many isolates that are harmless to humans, while others are highly pathogenic. Most notable among them are strains belonging to the pandemic O1/O139 serogroup lineage, which contains the causative agents of cholera. The environmental selective regimes that led to this ersity are key to understanding how pathogens evolve in environmental reservoirs. A local population of V. cholerae and its close relative Vibrio metoecus from a coastal pond and lagoon system was extensively s led during two consecutive months across four size fractions (480 isolates). In stark contrast to previous studies, the observed population was highly clonal, with 60% of V. cholerae isolates falling into one of five clonal complexes, which varied in abundance in the short temporal scale s led. V. cholerae clonal complexes had significantly different distributions across size fractions and the two environments s led, the pond and the lagoon. Sequencing the genomes of 20 isolates representing these five V. cholerae clonal complexes revealed different evolutionary trajectories, with considerable variations in gene content with potential ecological significance. Showing genotypic differentiation and differential spatial distribution, the dominant clonal complexes are likely ecologically ergent. Temporal variation in the relative abundance of these complexes suggests that transient blooms of specific clones could dominate local ersity. IMPORTANCE Vibrio cholerae is commonly found in coastal areas worldwide, with only a single group of this bacterium capable of causing severe cholera outbreaks. However, the potential to evolve the ability to cause disease exists in many strains of this species in its aquatic reservoir. Understanding how pathogenic bacteria evolve requires the study of their natural environments. By extensive s ling in a geographically restricted location in the United States, we found that most cells of a V. cholerae population belong to only a small number of strains. Analysis of their genome composition and spatial distribution indicates differential environmental adaptations between these strains. Other strains exist in smaller numbers, and the population was found to be temporally varied. This suggests frequent bloom and collapse cycles on a time scale of weeks. These population dynamics make it possible that more virulent strains could stochastically rise to large numbers, allowing for infection to occur.
Publisher: Cold Spring Harbor Laboratory
Date: 23-06-2023
DOI: 10.1101/2023.06.20.545838
Abstract: Eukaryotic phytoplankton, also known as algae, form the basis of marine food webs and are responsible for most of marine carbon sequestration when their dead biomass sinks to the ocean floor. Living algae must regulate their vertical movement in the ocean to balance access to light at the surface and nutrients in deeper layers. This can be achieved by motility, as in most green algae, or by changing cell size and composition, as in non-motile species like diatoms. However, motility-independent sinking velocities, as defined by Stokes’ law remain largely unknown, and it is unclear if motile species also adjust their cell size and composition in response to environmental changes. Here, we directly quantify single-cell mass and volume to calculate sinking velocity according to Stokes’ law in erse clades of unicellular marine microalgae under different nutrient conditions. We find species vary in cell density by % and in volume by %, resulting in sinking velocities that range from 0.2 to 12.8 μm/s. We observe ex les of motile dinoflagellate and green algal species where nutrient limitation causes cells to increase their sinking velocity by changing cell mass rather than volume, while a diatom species did not respond to nutrient limitation. We also find that single-cell sinking velocities display significant intraspecies heterogeneity, but only ∼50% of this heterogeneity is accounted for by variation in cell volume. Overall, our work reveals unexpected biophysical responses to nutrient limitation in motile algae and provides an approach for direct sinking velocity measurements for estimations of carbon fluxes in the oceans.
Publisher: Springer Science and Business Media LLC
Date: 06-10-2021
DOI: 10.1186/S40168-021-01151-5
Abstract: Microbial communities in both natural and applied settings reliably carry out myriads of functions, yet how stable these taxonomically erse assemblages can be and what causes them to transition between states remains poorly understood. We studied monthly activated sludge (AS) s les collected over 9 years from a full-scale wastewater treatment plant to answer how complex AS communities evolve in the long term and how the community functions change when there is a disturbance in operational parameters. Here, we show that a microbial community in activated sludge (AS) system fluctuated around a stable average for 3 years but was then abruptly pushed into an alternative stable state by a simple transient disturbance (bleaching). While the taxonomic composition rapidly turned into a new state following the disturbance, the metabolic profile of the community and system performance remained remarkably stable. A total of 920 metagenome-assembled genomes (MAGs), representing approximately 70% of the community in the studied AS ecosystem, were recovered from the 97 monthly AS metagenomes. Comparative genomic analysis revealed an increased ability to aggregate in the cohorts of MAGs with correlated dynamics that are dominant after the bleaching event. Fine-scale analysis of dynamics also revealed cohorts that dominated during different periods and showed successional dynamics on seasonal and longer time scales due to temperature fluctuation and gradual changes in mean residence time in the reactor, respectively. Our work highlights that communities can assume different stable states under highly similar environmental conditions and that a specific disturbance threshold may lead to a rapid shift in community composition.
Publisher: American Society for Microbiology
Date: 2012
DOI: 10.1128/AEM.06297-11
Abstract: Environmental Vibrio cholerae strains isolated from a coastal brackish pond (Oyster Pond, Woods Hole, MA) carried a novel filamentous phage, VCYϕ, which can exist as a host genome integrative form (IF) and a plasmid-like replicative form (RF). Outside the cell, the phage displays a morphology typical of Inovirus , with filamentous particles ∼1.8 μm in length and 7 nm in width. Four independent RF isolates had identical genomes, except for 8 single nucleotide polymorphisms clustered in two regions. The overall genome size is 7,103 bp with 11 putative open reading frames organized into three functional modules (replication, structure and assembly, and regulation). VCYϕ shares sequence similarity with other filamentous phages (including cholera disease-associated CTX) in a highly mosaic manner, indicating evolution by horizontal gene transfer and recombination. VCYϕ integrates in the vicinity of the putative translation initiation factor Sui1 in chromosome II of V. cholerae . A screen of 531 closely related host isolates showed that ∼40% harbored phages, with 27% and 13% carrying the IF and RF, respectively. The relative frequencies of the RF and IF differed among strains isolated from the pond or lagoon of Oyster Pond, suggesting that the host habitat influences intracellular phage biology. The overall high prevalence within the host population shows that filamentous phages can be an important component of the environmental biology of V. cholerae .
Publisher: Springer Science and Business Media LLC
Date: 21-04-2009
Abstract: Although integrons and their associated gene cassettes are present in ~10% of bacteria and can represent up to 3% of the genome in which they are found, very few have been properly identified and annotated in public databases. These genetic elements have been overlooked in comparison to other vectors that facilitate lateral gene transfer between microorganisms. By automating the identification of integron integrase genes and of the non-coding cassette-associated attC recombination sites, we were able to assemble a database containing all publicly available sequence information regarding these genetic elements. Specialists manually curated the database and this information was used to improve the automated detection and annotation of integrons and their encoded gene cassettes. ACID (annotation of cassette and integron data) can be searched using a range of queries and the data can be downloaded in a number of formats. Users can readily annotate their own data and integrate it into ACID using the tools provided. ACID is a community resource providing easy access to annotations of integrons and making tools available to detect them in novel sequence data. ACID also hosts a forum to prompt integron-related discussion, which can hopefully lead to a more universal definition of this genetic element.
Publisher: Wiley
Date: 06-02-2020
Abstract: Populations of the bacterium Vibrio cholerae consist of dozens of distinct lineages, with primarily (but not exclusively) members of the pandemic generating lineage capable of causing the diarrhoeal disease cholera. Assessing the composition and temporal dynamics of such populations requires extensive isolation efforts and thus only rarely covers large geographic areas or timeframes exhaustively. We developed a culture‐independent licon sequencing strategy based on the protein‐coding gene viuB (vibriobactin utilization) to study the structure of a V . cholerae population over the course of a summer. We show that the 26 co‐occurring V . cholerae lineages continuously compete for limited space on nutrient‐rich particles where only a few of them can grow to large numbers. Differential abundance of lineages between locations and size‐fractions associated with a particle‐attached or free‐swimming lifestyle could reflect adaptation to various environmental niches. In particular, a major V . cholerae lineage occasionally grows to large numbers on particles but remain undetectable using isolation‐based methods, indicating selective culturability for some members of the species. We thus demonstrate that isolation‐based studies may not accurately reflect the structure and complex dynamics of V . cholerae populations and provide a scalable high‐throughput method for both epidemiological and ecological approaches to studying this species.
Location: United States of America
No related grants have been discovered for Martin Polz.