62 research outputs found
Climate change effects on planktonic bacterial communities in the ocean: from structure and function to long-term and large scale observations.
No full textPlanktonic bacterial communities of marine environments can be considered to be affected by climate change through a set of direct and indirect effects. As direct effects of climate change, elevated temperature and ambient CO2 levels have to be taken into account. As indirect effects a large spectrum of impacts ranging from increased stratification of surface water, deoxygenation of subsurface water, increased occurrence of extreme weather events, and a changed food chain and nutrient regime resulting in a changed top down and bottom up control for bacterioplankton. All these direct and indirect effects will affect bacterial communities in a multifaceted way. Changes in the bacterial communities due to climate change impacts can be expected on all different taxonomic levels, i.e. from the clonal intraspecies level to the phylum level. The focus of the article will be on the evaluation of bacterioplankton observations over time and space and along climate gradients in the frame of environmental parameters allowing modelling with respect to climate change scenarios. A specific emphasis will be on bacterioplankton analysis based on analysis of samples of the Continuous Plankton Recorder Archive. This sample archive allowed insights into particle associated bacteria of coastal environments over more than the last 60 years. Beside effects of climate change effectors on bacterial growth and community composition, effects of climate change on bacteria-mediated marine biogeochemical cycling and potential hazards by increased abundance of pathogenic bacteria such as Vibrio cholerae will be considered
Effects of Global Warming on Vibrio Ecology.
No full textVibrio-related infections are increasing worldwide both in humans and aquatic animals. Rise in global sea surface temperature (SST), which is approximately 1 °C higher now than 140 years ago and is one of the primary physical impacts of global warming, has been linked to such increases. In this chapter, major known effects of increasing SST on the biology and ecology of vibrios are described. They include the effects on bacterial growth rate, both in the field and in laboratory, culturability, expression of pathogenicity traits, and interactions with aquatic organisms and abiotic surfaces. Special emphasis is given to the effect of ocean warming on Vibrio interactions with zooplankters, which represent one of the most important aquatic reservoirs for these bacteria. The reported findings highlight the biocomplexity of the interactions between vibrios and their natural environment in a climate change scenario, posing the need for interdisciplinary studies to properly understand the connection between ocean warming and persistence and spread of vibrios in sea waters and the epidemiology of the diseases they cause
The role of micro-organisms in the ecological connectivity of running waters
No full textPusch M, Fiebig D, Brettar I, et al. The role of micro-organisms in the ecological connectivity of running waters. Freshwater Biology. 1998;40(3):453-495
Denitrifikation in der Wassersäule der Zentralen Ostsee : Regulationsfaktoren und mikrobiologische Aspekte = Denitrification in the water column of the Central Baltic : Regulatory Factors and Microbiological Aspects
No full textIm Sommer 1986 und 1987 wurden Untersuchungen zur Denitrifikation in der Wassersäule der zentralen Ostsee durchgeführt Schwerpunkt der Untersuchungen war, die regulierenden Mechanismen der Denitrifikation zu erforschen. Als Untersuchungsgebiete dienten das zentral gelegene Gotlandtief und die im Norden gelegene Station T.
- Denitrifikationsraten wurden mit Hilfe der Azetylenblockmethode erfaßt. Die ermittelten Raten lagen zwischen 13,8 und 110 nmol N/l x d.
- Vor dem Hintergrund der gängigen bakteriologischen Rahmenparameter wurde die Anzahl von Denitrifikanten und Nitratreduzierern erfaßt. Die Anzahl der heterotrophen Denitrifikanten in der Wassersäule bewegte sich zwischen ungefähr 50 und 2400 Bakterien pro ml.
- Es zeigte sich, daß die Denitrifikation in der Wassersäule der zentralen Ostsee, sowohl in Bezug auf die Umsatzraten, als auch die räumliche Ausdehnung durch den verfügbaren organischen Kohlenstoff limitiert war. Die geringe Verfügbarkeit schien die Denitrifikation im wesentlichen auf "energiereiche" Grenzschichten wie oxisch-anoxische und Sediment-Wasser-Grenzschichten zu beschränken.
- Für die Denitrifikation an der oxisch-anoxischen Grenzfläche konnte gezeigt weiden, daß autotrophe Denitrifikation unter Nutzung von reduzierten Schwefelverbindungen aus dem anoxischen Bereich als Elektronendonatoren einen bedeutenden Beitrag zu leisten vermag ("H2S-Denitrifikation")..
Nitrate elimination by denitrification in hardwood forest soils of the Upper Rhine floodplain – correlation with redox potential and organic matter
No full textDenitrification in floodplains is a major issue for river- and groundwater quality. In the Upper Rhine valley,
floodplain forests are about to be restored to serve as flood retention areas (polders). Besides flood attenuation
in downstream areas, improvement of water quality became recently a major goal for polder construction. Redox
potential monitoring was suggested as a means to support assessment of nitrogen elimination in future floodplains
by denitrification during controlled flooding. To elucidate the relationship between redox potential and denitrification,
experiments with floodplain soils and in situ measurements were done. Floodplain soil of two depth
profiles from a hardwood forest of the Upper Rhine valley was incubated anaerobically with continuous nitrate
supply. Reduction of nitrate was followed and compared with redox potential and organic matter content. The
redox potential under denitrifying conditions ranged from 10 to 300 mV. Redox potential values decreased with
increasing nitrate reduction rates and increasing organic matter content. Furthermore, a narrow correlation between
organicmatter and nitrate reduction was observed. Experiments were intended to help interpreting redox potentials
generated under in situ conditions as exemplified by in situ observations for the year 1999. Results obtained by
experiments and in situ observations showed that monitoring of redox potential could support management of the
flooding regime to optimize nitrogen retention by denitrification in future flood retention areas
Whole-genome enrichment provides deep insights into Vibrio cholerae metagenome from an African river
No full textThe detection and typing of Vibrio cholerae in natural aquatic environments encounter major methodological challenges related to the fact that the bacterium is often present in environmental matrices at very low abundance in nonculturable state. This study applied, for the first time to our knowledge, a whole-genome enrichment (WGE) and next generation sequencing (NGS) approach for direct genotyping and metagenomic analysis of low abundant V. cholerae DNA (<50 genome unit/L) from natural water collected in the Morogoro river (Tanzania). The protocol is based on the use of biotinylated RNA baits for target enrichment of V. cholerae metagenomic DNA via hybridization.
An enriched V. cholerae metagenome library was generated and sequenced on a Illumina MiSeq platform. Up to 1.8X107 bp (4.5x mean read depth) were found to map against V. cholerae reference genome sequences representing an increase of about 2500 times in target DNA coverage compared to theoretical calculations of performance for shotgun metagenomics. Analysis of metagenomic data revealed the presence of several V. cholerae virulence and virulence associated genes in river water including major virulence regions (e.g. CTX prophage and Vibrio pathogenicity island-1) and genetic markers of epidemic strains (e.g. O1-antigen biosynthesis gene cluster) that were not detectable by standard culture and molecular techniques. Overall, besides providing a powerful tool for direct genotyping of V. cholerae in complex environmental matrices this study provides a “proof of concept” on the methodological gap that might currently preclude a more comprehensive understanding of toxigenic V. cholerae emergence from natural aquatic environments
Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic
No full textClimate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet.
In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958–2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years
Influence of carbon availability on dentrification in the central Baltic Sea
No full textDenitrification was investigated in the Baltic proper at two stations with different conditions in the deep water. The Gotland Deep was examined as an example of a basin with anoxic, H2S‐containing deep water and station T was taken as an example of low‐oxygen (<0.2 ml liter−1), sulfide‐free deep water. Denitrification was measured by the acetylene blockage method; in addition, N2O reduction was followed in samples without acetylene. To shed light on the factors limiting denitrification, we compared in situ rates to denitrification after adding nitrate or electron donors. Denitrification was restricted to the layer of the oxic‐anoxic interface in the Gotland Deep and to the water layer near the sediment of station T. For both stations it could be shown that denitrification was not limited by nitrate availability. A lack of available organic C seemed to limit denitrification rates and growth of denitrifiers. As a result of C limitation in the water column, denitrification was restricted to energy‐rich interfaces. In the low‐oxygen water away from energy‐rich interfaces, the less C‐demanding nitrification‐denitrification coupling (NH4+ → N2O → N2) seemed to be favored. Denitrification in the water of the central Baltic seems to be subjected to strong variability due to changing C supply during the course of the year. However, limitation by C availability can be assumed for most of the year and should be taken into account in calculating the N budget of the Baltic
Nitrous oxide producing heterotrophic bacteria from the water column of the central Baltic: abundance and molecular identification
No full textThe water column of the Gotland Deep, a basin with anoxic deep water in the central Baltic, was investigated for its denitrifying microflora in comparison with various chemical, hydrographical and microbiological parameters including in situ denitrification rates. Abundance of denitrifying bacterid was determined by the MPN method using nutrient broth plus nitrate medium. As gas formation in inverted vials turned out to be a rather variable feature, N2O production was used to detect the presence of denitrifying bacteria. Using 4 different cultivation approaches, 77 N2O producing strains were isolated from the whole water column. Isolates were analyzed for their denitrifying capacity to form NO2-, N2O, and N2. Taxonomic identification of the strains was done by high resolution electrophoresis of their low-molecular-weight (LMW) RNA (5S rRNA and tRNA). The bulk of the isolated N2O producing strains (77 %) was identified by their LMW RNA pattern as Shewanella putrefaciens. All strains of this species produced N2O, and NO2- and about one third showed N2-formation. S. putrefaciens is considered the most abundant culturable denitrifier of the low oxygen water and the oxic-anoxic interface of the Gotland Deep
Long-term effects of ocean warming on the prokaryotic community: evidence from the vibrios
No full textThe long-term effects of ocean warming on prokaryotic communities are unknown because of lack of historical data. We overcame this gap by applying a retrospective molecular analysis to the bacterial community on formalin-fixed samples from the historical Continuous Plankton Recorder archive, which is one of the longest and most geographically extensive collections of marine biological samples in the world. We showed that during the last half century, ubiquitous marine bacteria of the Vibrio genus, including Vibrio cholerae, increased in dominance within the plankton-associated bacterial community of the North Sea, where an unprecedented increase in bathing infections related to these bacteria was recently reported. Among environmental variables, increased sea surface temperature explained 45% of the variance in Vibrio data, supporting the view that ocean warming is favouring the spread of vibrios and may be the cause of the globally increasing trend in their associated diseases
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