Bacterial community composition in Central European running waters examined by temperature gradient gel electrophoresis and sequence analysis of 16S rRNA genes

Seasonal effects of river flow on microbial community coalescence and diversity in a riverine network

Terrestrial microbial communities may take advantage of running waters and runoff to enter rivers and mix with aquatic microorganisms. However, the environmental factors governing the interchange of the microbial community within a watercourse and its surrounding environment and the composition of the resulting community are often underestimated. The present study investigated the effect of flow rate on the mixing of water, soil, sediment and biofilm at four sites along the Lancang River and one branch of the river in winter and summer and, in turn, the resultant changes in the microbial community within each habitat. 16S rRNA gene-based Illumina high-throughput sequencing illustrated that bacterial communities were apparently distinct among biofilm, water, soil and sediment. Biofilms had the lowest richness, Shannon diversity and evenness indices compared with other habitats, and those three indices in all habitats increased significantly from winter to summer. SourceTracker analysis showed a significant coalescence between the bacterial communities of sediment, water and biofilm samples at lower flow rates. Additionally, the proportion of Betaproteobacteria in sediment and biofilms increased with a decrease in flow rate, suggesting the flow rate had a strong impact on microbial community composition and exchange among aquatic habitats. These results were further confirmed by a Mantel test and linear regression analysis. Microbial communities in all samples exhibited a significant but very weak distance-decay relationship (r = 0.093, P = 0.024). Turbidity played a much more important role on water bacterial community structure in summer (i.e. rainy season) (BIOENV, r = 0.92). Together, these results suggest that dispersal is an important factor affecting bacterial community structure in this system.

Rapid and Stable Microbial Community Assembly in the Headwaters of a Third-Order Stream

Small streams and their headwaters are key sources of microbial diversity in fluvial systems and serve as an entry point for bacteria from surrounding environments. Community assembly processes occurring in these streams shape downstream population structure and nutrient cycles. To elucidate the development and stability of microbial communities along the length of a first- through third-order stream, fine-scale temporal and spatial sampling regimes were employed along McNutt Creek in Athens, GA, USA. 16S rRNA amplicon libraries were constructed from samples collected on a single day from 19 sites spanning the first 16.76 km of the stream. To provide context for this spatial study and evaluate temporal variability, selected sites at the stream's upper, mid, and lower reaches were sampled daily for 5 days preceding and following the spatial study. In a second study, three sites at and near the creek's headwaters were sampled daily for 11 days to understand initial bacterioplankton community assembly. Both studies revealed decreasing alpha and beta diversity with increasing downstream distance. These trends were accompanied by the enrichment of a small fraction of taxa found at low abundance in headwater-proximal sites. Similar sets of taxa consistently increased in relative abundance in downstream samples over time scales ranging from 1 day to 1 year, many of which belong to clades known to be abundant in freshwater environments. These results underpin the importance of headwaters as the site of rapid in-stream selection that results in the reproducible establishment of a highly stable community of freshwater riverine bacteria.IMPORTANCE Headwater streams are critical introduction points of microbial diversity for larger connecting rivers and play key roles in the establishment of taxa that partake in in-stream nutrient cycling. We examined the microbial community composition of a first- through third-order stream using fine-scale temporal and spatial regimes. Our results show that the bacterioplankton community develops rapidly and predictably from the headwater population with increasing total stream length. Along the length of the stream, the microbial community exhibits substantial diversity loss and enriches repeatedly for select taxa across days and years, although the relative abundances of individual taxa vary over time and space. This repeated enrichment of a stable stream community likely contributes to the stability and flexibility of downstream communities.

River water analysis using a multiparametric approach: Portuguese river as a case study

The Ave River in northern Portugal has a history of riverbanks and water quality degradation. The river water quality was assessed by physicochemical, biological (macroinvertebrates) and microbiological (Enterococcus spp. and Escherichia coli) parameters in six locations (A-F, point A being the nearest to the source) throughout its course during a year. Epilithic biofilms were studied through polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Antimicrobial susceptibility testing helped with selecting isolates (n = 149 E. coli and n = 86 enterococci) for further genetic characterization. Pursuant to physicochemical and macroinvertebrates-based parameters, the river water was of reasonable quality according to European legislation (Directive 2000/60/EC). However, the microbiological analysis showed increased fecal contamination downstream from point C. At point D, four carbapenem-resistant E. coli isolates were recovered. Paradoxically, point D was classified as a point of 'Good Water Quality' according to macroinvertebrates results. Point F presented the highest contamination level and incidence of multidrug-resistant (MDR) isolates in the water column (13 MDR enterococci out of 39 and 33 MDR E. coli out of 97). Epilithic biofilms showed higher diversity in pristine points (A and B). Thus, biological and microbiological parameters used to assess the water quality led to divergent results; an outcome that reinforces the need for a holistic evaluation.

Temperature sensitivity of biodegradable dissolved organic carbon increases with elevating humification degree in subtropical rivers

Biodegradable dissolved organic carbon (BDOC) plays a key role in C cycle in inland waters. However, the magnitude of temperature sensitivity (Q₁₀ value) of BDOC is still unclear, and the effect of DOC quality on Q₁₀ value of BDOC is not well verified in these aquatic systems. Here, we used a laboratory incubation experiment to determine the Q₁₀ value of BDOC in 57 rivers in the Three Gorges Reservoir area, China, and then tested whether C quality-temperature hypothesis could be applied to BDOC in inland waters. We observed approximately twofold variations in Q₁₀ values of BDOC (1.42-2.67) in these rivers. Moreover, the tight positive relationship between the Q₁₀ values of BDOC and DOC humification index indicated the applicability of C quality-temperature hypothesis in subtropical rivers. In addition, the Q₁₀ values of BDOC exhibited a negative relationship with pH. These findings suggest that DOC quality and pH are powerful predictors of temperature sensitivity of BDOC in subtropical rivers. In conclusion, our results would help to improve the C models and predict the feedback between climate warming and C dynamics in inland waters.

Sediment bacteria in an urban stream: Spatiotemporal patterns in community composition

Sediment bacterial communities play a critical role in biogeochemical cycling in lotic ecosystems. Despite their ecological significance, the effects of urban discharge on spatiotemporal distribution of bacterial communities are understudied. In this study, we examined the effect of urban discharge on the spatiotemporal distribution of stream sediment bacteria in a northeast Ohio stream. Water and sediment samples were collected after large storm events (discharge > 100 m) from sites along a highly impacted stream (Tinkers Creek, Cuyahoga River watershed, Ohio, USA) and two reference streams. Although alpha (α) diversity was relatively constant spatially, multivariate analysis of bacterial community 16S rDNA profiles revealed significant spatial and temporal effects on beta (β) diversity and community composition and identified a number of significant correlative abiotic parameters. Clustering of upstream and reference sites from downstream sites of Tinkers Creek combined with the dominant families observed in specific locales suggests that environmentally-induced species sorting had a strong impact on the composition of sediment bacterial communities. Distinct groupings of bacterial families that are often associated with nutrient pollution (i.e., Comamonadaceae, Rhodobacteraceae, and Pirellulaceae) and other contaminants (i.e., Sphingomonadaceae and Phyllobacteriaceae) were more prominent at sites experiencing higher degrees of discharge associated with urbanization. Additionally, there were marked seasonal changes in community composition, with individual taxa exhibiting different seasonal abundance patterns. However, spatiotemporal variation in stream conditions did not affect bacterial community functional profiles. Together, these results suggest that local environmental drivers and niche filtering from discharge events associated with urbanization shape the bacterial community structure. However, dispersal limitations and interactions among other species likely play a role as well.

A comparative hierarchical analysis of bacterioplankton and biofilm metacommunity structure in an interconnected pond system

It is unknown whether bacterioplankton and biofilm communities are structured by the same ecological processes, and whether they influence each other through continuous dispersal (known as mass effects). Using a hierarchical sampling approach we compared the relative importance of ecological processes structuring the dominant fraction (relative abundance ≥0.1%) of bacterioplankton and biofilm communities from three microhabitats (open water, Nuphar and Phragmites sites) at within- and among-pond scale in a set of 14 interconnected shallow ponds. Our results demonstrate that while bacterioplankton and biofilm communities are highly distinct, a similar hierarchy of ecological processes is acting on them. For both community types, most variation in community composition was determined by pond identity and environmental variables, with no effect of space. The highest β-diversity within each community type was observed among ponds, while microhabitat type (Nuphar, Phragmites, open water) significantly influenced biofilm communities but not bacterioplankton. Mass effects among bacterioplankton and biofilm communities were not detected, as suggested by the absence of within-site covariation of biofilm and bacterioplankton communities. Both biofilm and plankton communities were thus highly structured by environmental factors (i.e., species sorting), with among-lake variation being more important than within-lake variation, whereas dispersal limitation and mass effects were not observed.

Microbial responses to polycyclic aromatic hydrocarbon contamination in temporary river sediments: Experimental insights

Temporary rivers are characterized by dry-wet phases and represent an important water resource in semi-arid regions worldwide. The fate and effect of contaminants have not been firmly established in temporary rivers such as in other aquatic environments. In this study, we assessed the effects of sediment amendment with Polycyclic Aromatic Hydrocarbons (PAHs) on benthic microbial communities. Experimental microcosms containing natural (Control) and amended sediments (2 and 20 mg PAHs kg(-1) were incubated for 28 days. The PAH concentrations in sediments were monitored weekly together with microbial community structural (biomass and phylogenetic composition by TGGE and CARD-FISH) and functional parameters (ATP concentration, community respiration rate, bacterial carbon production rate, extracellular enzyme activities). The concentration of the PAH isomers did not change significantly with the exception of phenanthrene. No changes were observed in the TGGE profiles, whereas the occurrence of Alpha- and Beta-Proteobacteria was significantly affected by the treatments. In the amended sediments, the rates of carbon production were stimulated together with aminopeptidase enzyme activity. The community respiration rates showed values significantly lower than the Control after 1 day from the amendment then recovering the Control values during the incubation. A negative trend between the respiration rates and ATP concentration was observed only in the amended sediments. This result indicates a potential toxic effect on the oxidative phosphorylation processes. The impoverishment of the energetic resources that follows the PAH impact may act as a domino on the flux of energy from prokaryotes to the upper level of the trophic chain, with the potential to alter the temporary river functioning.

Spatiotemporal dynamics and determinants of planktonic bacterial and microeukaryotic communities in a Chinese subtropical river

The spatiotemporal distribution of microbial diversity, community composition, and their major drivers are fundamental issues in microbial ecology. In this study, the planktonic bacterial and microeukaryotic communities of the Jiulong River were investigated across both wet and dry seasons by using denaturing gradient gel electrophoresis (DGGE). We found evidence of temporal change between wet and dry seasons and distinct spatial patterns of bacterial and microeukaryotic communities. Both bacterial and microeukaryotic communities were strongly correlated with temperature, NH4-N, PO4-P, and chlorophyll a, and these environmental factors were significant but incomplete predictors of microbial community composition. Local environmental factors combined with spatial and temporal factors strongly controlled both bacterial and microeukaryotic communities in complex ways, whereas the direct influence of spatial and temporal factors appeared to be relatively small. Path analysis revealed that the microeukaryotic community played key roles in shaping bacterial community composition, perhaps through grazing effects and multiple interactions. Both Betaproteobacteria and Actinobacteria were the most dominant and diverse taxa in bacterial communities, while the microeukaryotic communities were dominated by Ciliophora (zooplankton) and Chlorophyta (phytoplankton). Our results demonstrated that both bacterial and microeukaryotic communities along the Jiulong River displayed a distinct spatiotemporal pattern; however, microeukaryotic communities exhibited a stronger distance-decay relationship than bacterial communities and their spatial patterns were mostly driven by local environmental variables rather than season or spatial processes of the river. Therefore, we have provided baseline data to support further research on river microbial food webs and integrating different microbial groups into river models.

Quantifying the effects of geographical and environmental factors on distribution of stream bacterioplankton within nature reserves of Fujian, China

Bacterioplankton are important components of freshwater ecosystems and play essential roles in ecological functions and processes; however, little is known about their geographical distribution and the factors influencing their ecology, especially in stream ecosystems. To examine how geographical and environmental factors affect the composition of bacterioplankton communities, we used denaturing gradient gel electrophoresis and clone sequencing to survey bacterioplankton communities in 31 samples of streamwater from seven nature reserves in Fujian province, southeast China. Our results revealed that dominant bacterioplankton communities exhibited a distinct geographical pattern. Further, we provided evidence for distance decay relationships in bacterioplankton community similarity and found similar community gradients in response to elevation and latitude. Both redundancy analyses and Mantel tests showed that bacterioplankton community composition was significantly correlated with both environmental (electrical conductivity, total phosphorus, and PO4-P) and geographical factors (latitude, longitude, and elevation). Variance partitioning further showed that the joint effect of geographical and environmental factors explained the largest proportion of the variation in distribution of bacterioplankton communities (13.6 %), followed by purely geographical factors (11.2 %), and purely environmental factors (0.6 %). The Betaproteobacteria were the most common taxa in the streams, followed by Firmicutes and Gammaproteobacteria. Therefore, our results suggest that the biogeographical patterns of stream bacterioplankton communities across the Fujian nature reserves are more influenced by geographical factors than by local physicochemical properties.

Seasonal variations and resilience of bacterial communities in a sewage polluted urban river

The Zenne River in Brussels (Belgium) and effluents of the two wastewater treatment plants (WWTPs) of Brussels were chosen to assess the impact of disturbance on bacterial community composition (BCC) of an urban river. Organic matters, nutrients load and oxygen concentration fluctuated highly along the river and over time because of WWTPs discharge. Tag pyrosequencing of bacterial 16S rRNA genes revealed the significant effect of seasonality on the richness, the bacterial diversity (Shannon index) and BCC. The major grouping: -winter/fall samples versus spring/summer samples- could be associated with fluctuations of in situ bacterial activities (dissolved and particulate organic carbon biodegradation associated with oxygen consumption and N transformation). BCC of the samples collected upstream from the WWTPs discharge were significantly different from BCC of downstream samples and WWTPs effluents, while no significant difference was found between BCC of WWTPs effluents and the downstream samples as revealed by ANOSIM. Analysis per season showed that allochthonous bacteria brought by WWTPs effluents triggered the changes in community composition, eventually followed by rapid post-disturbance return to the original composition as observed in April (resilience), whereas community composition remained altered after the perturbation by WWTPs effluents in the other seasons.

Rhodoferax saidenbachensis sp. nov., a psychrotolerant, very slowly growing bacterium within the family Comamonadaceae, proposal of appropriate taxonomic position of Albidiferax ferrireducens strain T118T in the genus Rhodoferax and emended description of the genus Rhodoferax

A Gram-stain-negative, oxidase and phosphatase-positive and catalase-negative, short rod-shaped bacterium was isolated from sediment of a drinking water reservoir in Germany. Based on 16S rRNA gene sequence and phenotypic properties, the bacterium belongs to the genus Rhodoferax within the family Comamonadaceae. The new taxon differed from related species mainly with respect to its fatty acid composition, low growth temperature, lack of pigments in young cultures and ability to utilize glycerol and d-mannose but not urea. The major fatty acids were C16 : 1ω7c and/or iso-C15 : 0 2-OH, C16 : 0, and C18 : 1ω7c. The only ubiquinone detected was ubiquinone Q-8. The DNA G+C content was 60.3-61 mol%. Because of the phenotypic and genotypic differences from the most closely related taxa, the new strain represents a novel species for which the name Rhodoferax saidenbachensis sp. nov. is proposed. The type strain is ED16(T) ( = CCUG 57711(T) = ATCC BAA-1852(T) = DSM 22694(T)). An emended description of the genus Rhodoferax is proposed. Based on the results of this study, strain T118(T) (Albidiferax ferrireducens) is properly placed in the genus Rhodoferax as Rhodoferax ferrireducens.

Bacterial community composition and extracellular enzyme activity in temperate streambed sediment during drying and rewetting

Droughts are among the most important disturbance events for stream ecosystems; they not only affect stream hydrology but also the stream biota. Although desiccation of streams is common in Mediterranean regions, phases of dryness in headwaters have been observed more often and for longer periods in extended temperate regions, including Central Europe, reflecting global climate change and enhanced water withdrawal. The effects of desiccation and rewetting on the bacterial community composition and extracellular enzyme activity, a key process in the carbon flow of streams and rivers, were investigated in a typical Central European stream, the Breitenbach (Hesse, Germany). Wet streambed sediment is an important habitat in streams. It was sampled and exposed in the laboratory to different drying scenarios (fast, intermediate, slow) for 13 weeks, followed by rewetting of the sediment from the fast drying scenario via a sediment core perfusion technique for 2 weeks. Bacterial community structure was analyzed using CARD-FISH and TGGE, and extracellular enzyme activity was assessed using fluorogenic model substrates. During desiccation the bacterial community composition shifted toward composition in soil, exhibiting increasing proportions of Actinobacteria and Alphaproteobacteria and decreasing proportions of Bacteroidetes and Betaproteobacteria. Simultaneously the activities of extracellular enzymes decreased, most pronounced with aminopeptidases and less pronounced with enzymes involved in the degradation of polymeric carbohydrates. After rewetting, the general ecosystem functioning, with respect to extracellular enzyme activity, recovered after 10 to 14 days. However, the bacterial community composition had not yet achieved its original composition as in unaffected sediments within this time. Thus, whether the bacterial community eventually recovers completely after these events remains unknown. Perhaps this community undergoes permanent changes, especially after harsh desiccation, followed by loss of the specialized functions of specific groups of bacteria.

Sequencing ancient calcified dental plaque shows changes in oral microbiota with dietary shifts of the Neolithic and Industrial revolutions

The importance of commensal microbes for human health is increasingly recognized, yet the impacts of evolutionary changes in human diet and culture on commensal microbiota remain almost unknown. Two of the greatest dietary shifts in human evolution involved the adoption of carbohydrate-rich Neolithic (farming) diets (beginning ∼10,000 years before the present) and the more recent advent of industrially processed flour and sugar (in ∼1850). Here, we show that calcified dental plaque (dental calculus) on ancient teeth preserves a detailed genetic record throughout this period. Data from 34 early European skeletons indicate that the transition from hunter-gatherer to farming shifted the oral microbial community to a disease-associated configuration. The composition of oral microbiota remained unexpectedly constant between Neolithic and medieval times, after which (the now ubiquitous) cariogenic bacteria became dominant, apparently during the Industrial Revolution. Modern oral microbiotic ecosystems are markedly less diverse than historic populations, which might be contributing to chronic oral (and other) disease in postindustrial lifestyles.

Effects of wet and dry seasons on the aquatic bacterial community structure of the Three Gorges Reservoir

This study investigated effects of wet and dry seasons on the bacterial community structure of the Three Gorges Reservoir by using denaturing gradient gel electrophoresis analysis of the PCR-amplified bacterial 16S rRNA gene. Bacterial diversity, as determined by the Shannon index, the Simpson's index, and the Richness, dramatically changed in between the dry and wet seasons. The changes in the diversity and relative abundance of microbial populations among the five sites during the wet season have become more marked than those observed during the dry season. Furthermore, cluster analysis also showed these changes. The phylogenetic analysis indicated that Betaproteobacteria is the dominant population, followed by Actinobacterium, in both the wet season and dry season. The water quality parameters were quite stable at all five sites during the same season but noticeably varied from season to season. Canonical correspondence analysis also indicated that the changes in the bacterial community composition were primarily correlated with the variations in temperature, transparency, and the concentrations of NH4 (+)-N. Slight changes in bacterial community composition among the five sites during the dry season were correlated with different environments. However, during the wet season, major changes were correlated not only with environments, but also it may be associated with the bacterial populations from the surrounding areas and tributaries of the Three Gorges Reservoir.

Molecular fingerprinting of cyanobacteria from river biofilms as a water quality monitoring tool

Benthic cyanobacterial communities from Guadarrama River (Spain) biofilms were examined using temperature gradient gel electrophoresis (TGGE), comparing the results with microscopic analyses of field-fixed samples and the genetic characterization of cultured isolates from the river. Changes in the structure and composition of cyanobacterial communities and their possible association with eutrophication in the river downstream were studied by examining complex TGGE patterns, band extraction, and subsequent sequencing of 16S rRNA gene fragments. Band profiles differed among sampling sites depending on differences in water quality. The results showed that TGGE band richness decreased in a downstream direction, and there was a clear clustering of phylotypes on the basis of their origins from different locations according to their ecological requirements. Multivariate analyses (cluster analysis and canonical correspondence analysis) corroborated these differences. Results were consistent with those obtained from microscopic observations of field-fixed samples. According to the phylogenetic analysis, morphotypes observed in natural samples were the most common phylotypes in the TGGE sequences. These phylotypes were closely related to Chamaesiphon, Aphanocapsa, Pleurocapsa, Cyanobium, Pseudanabaena, Phormidium, and Leptolyngbya. Differences in the populations in response to environmental variables, principally nutrient concentrations (dissolved inorganic nitrogen and soluble reactive phosphorus), were found. Some phylotypes were associated with low nutrient concentrations and high levels of dissolved oxygen, while other phylotypes were associated with eutrophic-hypertrophic conditions. These results support the view that once a community has been characterized and its genetic fingerprint obtained, this technique could be used for the purpose of monitoring rivers.

Petroleum-influenced beach sediments of the Campeche Bank, Mexico: diversity and bacterial community structure assessment

The bacterial diversity and community structure were surveyed in intertidal petroleum-influenced sediments of ≈ 100 km of a beach, in the southern Gulf of Mexico. The beach was divided in twenty sampling sites according to high, moderate and low petroleum influence. Densities of cultured heterotrophic (HAB) and hydrocarbon degrading bacteria (HDB) were highly variable in sediments, with little morphological assortment in colonies. PCR-RISA banding patterns differentiated distinct communities along the beach, and the bacterial diversity changed inversely to the degree of petroleum hydrocarbon influence: the higher TPH concentration, the lower genotype diversity. Seven DNA sequences (Genbank EF191394 -EF191396 and EF191398 -EF191401) were affiliated to uncultured members of Gemmatimonas, Acidobacterium, Desulfobacteraceae, Rubrobacterales, Actinobacterium and the Fibrobacteres/Acidobacteria group; all the above taxa are known for having members with active roles in biogeochemical transformations. The remaining sequences (EF191388 - EF191393 and EF191397) affiliated to Pseudoalteromonas, and to oil-degrading genera such as Pseudomonas, Vibrio and Marinobacter, being the last one an obligate oil-degrading bacterium. An exchange of bacteria between the beach and the oil seep environment, and the potential cleaning-up role of bacteria at the southern Gulf of Mexico are discussed.

Seasonal and successional influences on bacterial community composition exceed that of protozoan grazing in river biofilms

The effects of protozoa (heterotrophic flagellates and ciliates) on the morphology and community composition of bacterial biofilms were tested under natural background conditions by applying size fractionation in a river bypass system. Confocal laser scanning microscopy (CLSM) was used to monitor the morphological structure of the biofilm, and fingerprinting methods (single-stranded conformation polymorphism [SSCP] and denaturing gradient gel electrophoresis [DGGE]) were utilized to assess changes in bacterial community composition. Season and internal population dynamics had a greater influence on the bacterial biofilm than the presence of protozoa. Within this general framework, bacterial area coverage and microcolony abundance were nevertheless enhanced by the presence of ciliates (but not by the presence of flagellates). We also found that the richness of bacterial operational taxonomic units was much higher in planktonic founder communities than in the ones establishing the biofilm. Within the first 2 h of colonization of an empty substrate by bacteria, the presence of flagellates additionally altered their biofilm community composition. As the biofilms matured, the number of bacterial operational taxonomic units increased when flagellates were present in high abundances. The additional presence of ciliates tended to at first reduce (days 2 to 7) and later increase (days 14 to 29) bacterial operational taxonomic unit richness. Altogether, the response of the bacterial community to protozoan grazing pressure was small compared to that reported in planktonic studies, but our findings contradict the assumption of a general grazing resistance of bacterial biofilms toward protozoa.

Biotechnologies for the management of genetic resources for food and agriculture

In recent years, the land area under agriculture has declined as also has the rate of growth in agricultural productivity while the demand for food continues to escalate. The world population now stands at 7 billion and is expected to reach 9 billion in 2045. A broad range of agricultural genetic diversity needs to be available and utilized in order to feed this growing population. Climate change is an added threat to biodiversity that will significantly impact genetic resources for food and agriculture (GRFA) and food production. There is no simple, all-encompassing solution to the challenges of increasing productivity while conserving genetic diversity. Sustainable management of GRFA requires a multipronged approach, and as outlined in the paper, biotechnologies can provide powerful tools for the management of GRFA. These tools vary in complexity from those that are relatively simple to those that are more sophisticated. Further, advances in biotechnologies are occurring at a rapid pace and provide novel opportunities for more effective and efficient management of GRFA. Biotechnology applications must be integrated with ongoing conventional breeding and development programs in order to succeed. Additionally, the generation, adaptation, and adoption of biotechnologies require a consistent level of financial and human resources and appropriate policies need to be in place. These issues were also recognized by Member States at the FAO international technical conference on Agricultural Biotechnologies for Developing Countries (ABDC-10), which took place in March 2010 in Mexico. At the end of the conference, the Member States reached a number of key conclusions, agreeing, inter alia, that developing countries should significantly increase sustained investments in capacity building and the development and use of biotechnologies to maintain the natural resource base; that effective and enabling national biotechnology policies and science-based regulatory frameworks can facilitate the development and appropriate use of biotechnologies in developing countries; and that FAO and other relevant international organizations and donors should significantly increase their efforts to support the strengthening of national capacities in the development and appropriate use of pro-poor agricultural biotechnologies.

Influence of deglaciation on microbial communities in marine sediments off the coast of Svalbard, Arctic Circle

Increases in global temperatures have been shown to enhance glacier melting in the Arctic region. Here, we have evaluated the effects of meltwater runoff on the microbial communities of coastal marine sediment located along a transect of Temelfjorden, in Svalbard. As close to the glacier front, the sediment properties were clearly influenced by deglaciation. Denaturing gradient gel electrophoresis profiles showed that the sediment microbial communities of the stations of glacier front (stations 188-178) were distinguishable from that of outer fjord region (station 176). Canonical correspondence analysis indicated that total carbon and calcium carbonate in sediment and chlorophyll a in bottom water were key factors driving the change of microbial communities. Analysis of 16S rRNA gene clone libraries suggested that microbial diversity was higher within the glacier-proximal zone (station 188) directly affected by the runoffs than in the outer fjord region. While the crenarchaeotal group I.1a dominated at station 176 (62%), Marine Benthic Group-B and other Crenarchaeota groups were proportionally abundant. With regard to the bacterial community, alpha-Proteobacteria and Flavobacteria lineages prevailed (60%) at station 188, whereas delta-Proteobacteria (largely sulfate-reducers) predominated (32%) at station 176. Considering no clone sequences related to sulfate-reducers, station 188 may be more oxic compared to station 176. The distance-wise compositional variation in the microbial communities is attributable to their adaptations to the sediment environments which are differentially affected by melting glaciers.

Construction of river model biofilm for assessing pesticide effects

Due to the high importance of biofilms on river ecosystems, assessment of pesticides' adverse effects is necessary but is impaired by high variability and poor reproducibility of both natural biofilms and those developed in the laboratory. We constructed a model biofilm to evaluate the effects of pesticides, consisting in cultured microbial strains, Pedobacter sp. 7-11, Aquaspirillum sp. T-5, Stenotrophomonas sp. 3-7, Achnanthes minutissima N71, Nitzschia palea N489, and/or Cyclotella meneghiniana N803. Microbial cell numbers, esterase activity, chlorophyll-a content, and the community structure of the model biofilm were examined and found to be useful as biological factors for evaluating the pesticide effects. The model biofilm was formed through the cooperative interaction of bacteria and diatoms, and a preliminary experiment using the herbicide atrazine, which inhibits diatom growth, indicated that the adverse effect on diatoms inhibited indirectly the bacterial growth and activity and, thus, the formation of the model biofilm. Toxicological tests using model biofilms could be useful for evaluating the pesticide effects and complementary to studies on actual river biofilms.

Changes in pelagic bacteria communities due to leaf litter addition

In many limnetic systems, the input of allochthonous organic matter, e.g., leaf litter, is a substantial source of dissolved organic carbon (DOC) for pelagic bacteria, especially in fall and winter when autochthonous DOC production is low. However, relatively little is known about community changes of pelagic lake bacteria due to leaf litter input which includes both the release of leaf leachates and microorganisms from the leaf litter into the surrounding water. Therefore, we have experimentally studied the effects of different types of leaf litter (Betula pendula, Fagus silvatica, and Pinus silvestris) on the pelagic bacterial community composition by adding leaves to different treatments of epilimnic water samples (unfiltered, 0.2 µm and 5.0 µm-pre-filtered) from humic Lake Grosse Fuchskuhle (Northeastern Germany). The addition of leaf litter led to a significant increase in DOC concentration in lake water, and each leaf litter type produced significantly different amounts of DOC (p = <0.001) as well as of specific DOC fractions (p = <0.001), except of polysaccharides. DGGE banding patterns varied over time, between types of leaf litter, and among treatments. Bacteria belonging to known bacterial phylotypes in the southwest basin of Lake Grosse Fuchskuhle were frequently found and even persisted after leaf litter additions. Upon leaf litter addition, α-proteobacteria (Azospirillum, Novosphingobium, and Sphingopyxis) as well as β-proteobacteria (Curvibacter and Polynucleobacter) were enriched. Our results indicate that supply of leaf litter DOM shifted the bacterial community in the surrounding water towards specific phylotypes including species capable of assimilating the more recalcitrant DOC pools. Statistical analyses, however, show that DGGE banding patterns are not only affected by DOC pools but also by treatment. This indicates that biological factors such as source community and grazing may be also important for shifts in bacterial community structure following leaf litter input into different lakes.

Bacterial populations in epilithic biofilms along two oligotrophic rivers in the Tohoku region in Japan

Bacterial populations in epilithic biofilms collected from two distinct oligotrophic rivers of Japan were studied using denaturing gradient gel electrophoresis (DGGE). PCR-DGGE of the 16S rRNA gene and subsequent sequencing analysis suggested that in freshwater biofilms, members of the Cytophaga-Flavobacterium-Bacteroides (CFB) group were the most dominant, followed by those of alpha, beta, gamma, and delta-Proteobacteria; Leptospiraceae; and unidentified bacteria. Members of the CFB group, alpha-Proteobacteria, and cyanobacteria/plastid DNA were also detected from the biofilms collected from the estuary site, but the species in these samples differed from those detected in biofilms in the freshwater areas of the rivers. A comparison between the determined sequences revealed that similar bacterial species existed in biofilms at different sites of a river, and identical species existed in biofilms of distinct rivers. The results suggested that bacterial species in biofilms found in the estuary were different from those found in the freshwater areas of the rivers; however, the common bacterial species were distributed in biofilms collected from not only different sites along the same river but also sites in distinct oligotrophic rivers.

The effects of N:P ratio and nitrogen form on four major freshwater bacterial taxa in biofilms

Bacteria in freshwater systems play an important role in nutrient cycling through both assimilatory and dissimilatory processes. Biotic and abiotic components of the environment affect these transformations as does the stoichiometry of the nutrients. We examined responses of four major taxa of bacteria in biofilms subjected to various N:P molar ratios using either nitrate or ammonium as a nitrogen source. Fluorescent in situ hybridization was used to enumerate the Domain bacteria as well as the alpha-, beta-, and gamma-proteobacteria, and the Cytophaga-Flavobacteria cluster. Generally, bacterial responses to the treatments were limited. However, the Cytophaga-Flavobacteria and beta-proteobacteria both responded more to the ammonium additions than nitrate, whereas, the alpha-proteobacteria responded more to nitrate additions. The beta-proteobacteria also exhibited peak relative abundance at the highest N:P ratio. Nutrient concentrations were significantly different after the incubation period, and there were distinct changes in the stoichiometry of the microcosms with ammonium. We demonstrated that bacteria may play an important role in nutrient uptake, and transformation, and can have a dramatic effect on the nutrient stoichiometry of the surrounding water. However, although some taxa exhibited differences in response to ammonium and nitrate, the impact of nutrient stoichiometry on the abundance of the taxa examined was limited.

Isolation and genomic characterization of the first phage infecting Iodobacteria: ϕPLPE, a myovirus having a novel set of features

The aquatic phage ϕPLPE infects a bacterium of the genus Iodobacter that are common inhabitants of rivers, streams and canals that produce violacein-like pigments. Our characterization of ϕPLPE reveals it to be a small, contractile-tailed phage whose 47.5 kb genome sequence is phylogenetically distant from all previously characterized phages. The genome has a generally modular organization (e.g. replication/recombination, structure/morphogenesis, lysis/lysogeny) and approximately half of its 84 open reading frames have no known homologues. It behaves as a virulent phage under the host growth conditions we have employed and, with the exception of an anti-repressor (ant) homologue, the genome lacks all the genes associated with a lysogenic lifestyle. Thus, either ϕPLPE was once a temperate phage that has lost most of its lysogeny cassette or it is a virulent phage that acquired an ant-like gene presumably for some function other than the control of lysogeny. The ϕPLPE genome has few bacterial gene homologues with the interesting exception of a putative acylhydrolase (acylase). This function has been implicated in bacterial quorum sensing since it degrades homoserine-lactone signalling molecules and can disrupt or modulate quorum signalling from either the emitter or its competitors. ϕPLPE may be an example of a phage co-opting components of the bacterial quorum-sensing apparatus to its own advantage.

From extensive clone libraries to comprehensive DNA arrays for the efficient and simultaneous detection and identification of orchid mycorrhizal fungi

A DNA array was developed from extensive clone library sequence data sets for the assessment of dominant members of mycorrhizal fungi that associate with terrestrial orchid species. As a-proof-of-concept, the array was developed for the basidiomycetous mycorrhizal partners from three closely related perennial Orchis species, including Orchis anthropophora, O. militaris and O. purpurea. Based on internal transcribed spacer regions, oligonucleotides were developed for seven operational taxonomic units (OTUs; defined as groups of sequences sharing at least 97% sequence similarity), corresponding to members of the Tulasnellaceae family. In order to cover a broader spectrum of tulasnelloid fungi, oligonucleotides were as well developed for two subsets of closely related OTUs. The array was evaluated using multiple primer pairs. In addition, hybridization results were validated by recovery and sequencing of the hybridized amplicons as well as by hybridizing reference DNA samples. Considering the unlimited expansion possibilities of DNA arrays to include specific detector oligonucleotides for other and more microorganisms, the method described here has the major advantage that it provides a powerful, rapid and cost-effective way for the simultaneous detection and identification of a wide range of orchid mycorrhizae. The design, development and advantages of the array are discussed in relation to its potential for future research in mycorrhizal ecology.

Vertical distribution and diversity of sulfate-reducing prokaryotes in the Pearl River estuarine sediments, Southern China

The vertical distribution and diversity of sulfate-reducing prokaryotes (SRPs) in a sediment core from the Pearl River Estuary was reported for the first time. The profiles of methane and sulfate concentrations along the sediment core indicated processes of methane production/oxidation and sulfate reduction. Phospholipid fatty acids analysis suggested that sulfur-oxidizing bacteria (SOB) might be abundant in the upper layers, while SRPs might be distributed throughout the sediment core. Quantitative competitive-PCR analysis indicated that the ratios of SRPs to total bacteria in the sediment core varied from around 2-20%. Four dissimilatory sulfite reductase (dsrAB) gene libraries were constructed and analyzed for the top layer (0-6 cm), middle layer (18-24 cm), bottom layer (44-50 cm) and the sulfate-methane transition zone (32-42 cm) sediments. Most of the retrieved dsrAB sequences (80.9%) had low sequence similarity with known SRP sequences and formed deeply branching dsrAB lineages. Meanwhile, bacterial 16S rRNA gene analysis revealed that members of the Proteobacteria were predominant in these sediments. Putative SRPs within Desulfobacteriaceae, Syntrophaceae and Desulfobulbaceae of Deltaproteobacteria, and putative SOB within Epsilonproteobacteria were detected by the 16S rRNA gene analysis. Results of this study suggested a variety of novel SRPs in the Pearl River Estuary sediments.

Polynucleobacter cosmopolitanus sp. nov., free-living planktonic bacteria inhabiting freshwater lakes and rivers

Five heterotrophic, aerobic, catalase- and oxidase-positive, non-motile strains were characterized from freshwater habitats located in Austria, France, Uganda, P. R. China and New Zealand. The strains shared 16S rRNA gene similarities of >/=99.3 %. The novel strains grew on NSY medium over a temperature range of 10-35 degrees C (two strains also grew at 5 degrees C and one strain grew at 38 degrees C) and a NaCl tolerance range of 0.0-0.3 % (four strains grew up to 0.5 % NaCl). The predominant fatty acids were C(16 : 0), C(18 : 1)omega7c, C(12 : 0) 3-OH, and summed feature 3 (including C(16 : 1)omega7c). The DNA G+C content of strain MWH-MoIso2(T) was 44.9 mol%. Phylogenetic analysis of 16S rRNA gene sequences demonstrated that the five new strains formed a monophyletic cluster closely related to Polynucleobacter necessarius (96-97 % sequence similarity). This cluster also harboured other isolates as well as environmental sequences which have been obtained from several habitats. Investigations with taxon-specific FISH probes demonstrated that the novel bacteria dwell as free-living, planktonic cells in freshwater systems. Based on the revealed phylogeny and pronounced chemotaxonomic differences to P. necessarius (presence of >7 % C(12 : 0) 3-OH and absence of C(12 : 0) and C(12 : 0) 2-OH), the new strains are suggested to represent a novel species, for which the name Polynucleobacter cosmopolitanus sp. nov. is proposed. The type strain is MWH-MoIso2(T) (=DSM 21490(T)=CIP 109840(T)=LMG 25212(T)). The novel species belongs to the minority of described species of free-living bacteria for which both in situ data from their natural environments and culture-based knowledge are available.

Comparison of the structure and composition of bacterial communities from temperate and tropical freshwater ecosystems

We used a partial 16S rRNA sequencing approach to compare the structure and composition of the bacterial communities in three large, deep subalpine lakes in France with those of communities in six shallow tropical reservoirs in Burkina Faso. Despite the very different characteristics of these ecosystems, we found that their bacterial communities share the same composition in regard to the relative proportions of the different phyla, suggesting that freshwater environmental conditions lead to convergence in this composition. In the same way, we found no significant difference in the richness and diversity of the bacterial communities in France and Burkina Faso. We defined core and satellite operational taxonomic units (OTUs) (sequences sharing at least 98% identity) on the basis of their abundance and their geographical distribution. The core OTUs were found either ubiquitously or only in temperate or tropical and subtropical areas, and they contained more than 70% of all the sequences retrieved in this study. In contrast, satellite OTUs were characterized by having a more restricted geographical distribution and by lower abundance. Finally, the bacterial community composition of these freshwater ecosystems in France and Burkina Faso was markedly different, showing that the history of these ecosystems and regional environmental parameters have a greater impact on the relative abundances of the different OTUs in each bacterial community than the local environmental conditions.

Description of seven candidate species affiliated with the phylum Actinobacteria, representing planktonic freshwater bacteria

Actinobacteria comprise a substantial fraction of the bacterioplankton in freshwater lakes and streams. Numerous cultivation-independent investigations have retrieved actinobacterial 16S rRNA gene sequences from such habitats. The taxa detected in freshwater habitats are usually absent from terrestrial and marine systems. So far, none of the indigenous freshwater lineages is represented by a taxon with a validly published name. The seven organisms for which Candidatus status is described here were isolated from freshwater lakes and ponds located in tropical, subtropical and temperate climatic zones. Phylogenetic analyses demonstrated that they are affiliated with one of the actinobacterial lineages indigenous to freshwater bacterioplankton. The seven novel taxa could only be cultivated to date as mixed cultures that also contain non-actinobacterial strains. Due to the lack of pure cultures, I propose to establish the candidate species 'Candidatus Planktoluna difficilis', 'Candidatus Aquiluna rubra', 'Candidatus Flaviluna lacus', 'Candidatus Rhodoluna limnophila', 'Candidatus Rhodoluna planktonica', 'Candidatus Rhodoluna lacicola' and 'Candidatus Limnoluna rubra' for these taxa.

Influence of particle size on bacterial community structure in aquatic sediments as revealed by 16S rRNA gene sequence analysis

Bacterial communities associated with sediment particles were examined using PCR-denaturing gradient gel electrophoresis and 16S rRNA gene sequencing. Particle size influenced community structure, with attached bacterial assemblages separating into 63- to 125-, 125- to 1,000-, and 1,000- to 2,000-microm fractions. Differences were particularly pronounced for the Verrucomicrobia-Planctomycetes, whose numbers were significantly reduced on coarser particles.