Modification of a High-Throughput Automatic Microbial Cell Enumeration System for Shipboard Analyses.

In the age of ever-increasing "-omics" studies, the accurate and statistically robust determination of microbial cell numbers within often-complex samples remains a key task in microbial ecology. Microscopic quantification is still the only method to enumerate specific subgroups of microbial clades within complex communities by, for example, fluorescence in situ hybridization (FISH). In this study, we improved an existing automatic image acquisition and cell enumeration system and adapted it for usage at high seas on board an oceanographic research ship.

Winter bloom of a rare betaproteobacterium in the Arctic Ocean.

Extremely low abundance microorganisms (members of the "rare biosphere") are believed to include dormant taxa, which can sporadically become abundant following environmental triggers. Yet, microbial transitions from rare to abundant have seldom been captured in situ, and it is uncertain how widespread these transitions are. A bloom of a single ribotype (≥99% similarity in the 16S ribosomal RNA gene) of a widespread betaproteobacterium (Janthinobacterium sp.

Pathobiology of Mycoplasma suis.

Mycoplasma suis is an uncultivable bacterium lacking a cell wall that attaches to and may invade the red blood cells of pigs. M. suis infections occur worldwide and cause the pig industry serious economic losses due to the disease known as infectious anaemia of pigs or, historically, porcine eperythrozoonosis.

Comparison of bacterial communities on limnic versus coastal marine particles reveals profound differences in colonization.

Marine and limnic particles are hotspots of organic matter mineralization significantly affecting biogeochemical element cycling. Fluorescence in-situ hybridization and pyrosequencing of 16S rRNA genes were combined to investigate bacterial diversity and community composition on limnic and coastal marine particles > 5 and > 10 μm respectively. Limnic particles were more abundant (average: 1 × 10(7) l(-1)), smaller in size (average areas: 471 versus 2050 μm(2)) and more densely colonized (average densities: 7.

Fluorescence in situ hybridization (CARD-FISH) of microorganisms in hydrocarbon contaminated aquifer sediment samples.

Groundwater ecosystems are the most important sources of drinking water worldwide but they are threatened by contamination and overexploitation. Petroleum spills account for the most common source of contamination and the high carbon load results in anoxia and steep geochemical gradients. Microbes play a major role in the transformation of petroleum hydrocarbons into less toxic substances.

Suboptimal light conditions negatively affect the heterotrophy of Planktothrix rubescens but are beneficial for accompanying Limnohabitans spp.

We examined the effect of light on the heterotrophic activity of the filamentous cyanobacterium Planktothrix rubescens and on its relationship with the accompanying bacteria. In situ leucine uptake by bacteria and cyanobacteria was determined in a subalpine mesotrophic lake, and natural assemblages from the zone of maximal P. rubescens abundances were incubated for 2 days at contrasting light regimes (ambient, 100× increased, dark).

The bacterial community composition of the surface microlayer in a high mountain lake.

The existence of bacterioneuston in aquatic ecosystems is well established, but little is known about its composition and dynamics, particularly in lakes. The bacterioneuston underlies extreme conditions at the air-water boundary, which may influence its dynamics in a different way compared with the bacterioplankton. In this study, we assessed quantitative changes in major bacterial groups of the surface microlayer (SML) (upper 900 microm) and the underlying water (ULW) (0.

Multiple toxin production in the cyanobacterium microcystis: isolation of the toxic protease inhibitor cyanopeptolin 1020.

The isolation and structure of cyanopeptolin 1020 (hexanoic acid-Glu-N[-O-Thr-Arg-Ahp-Phe-N-Me-Tyr-Val-]) from a Microcystis strain is reported. Very potent picomolar trypsin inhibition (IC(50) = 670 pM) and low nanomolar values against human kallikrein (4.5 nM) and factor XIa (3.

Automated quantification and sizing of unbranched filamentous cyanobacteria by model-based object-oriented image analysis.

Quantification and sizing of filamentous cyanobacteria in environmental samples or cultures are time-consuming and are often performed by using manual or semiautomated microscopic analysis. Automation of conventional image analysis is difficult because filaments may exhibit great variations in length and patchy autofluorescence. Moreover, individual filaments frequently cross each other in microscopic preparations, as deduced by modeling.

A small population of planktonic Flavobacteria with disproportionally high growth during the spring phytoplankton bloom in a prealpine lake.

Bacterioplankton growth in temperate Lake Zurich (Switzerland) was studied during the spring phytoplankton bloom by in situ techniques and short-term dilution bioassays. A peak of chlorophyll a (Chl a) concentrations was followed by a rise of bacterial cell numbers and leucine assimilation rates, of the proportions of cells incorporating 5-bromo-2-deoxyuridine (BrdU), and of community net growth rates in dilution cultures. Incorporation of BrdU was low in Betaproteobacteria (2 +/- 1%), indicating that these bacteria did not incorporate the tracer.

Ecophysiological differences of betaproteobacterial populations in two hydrochemically distinct compartments of a subtropical lagoon.

We studied the population sizes and substrate incorporation patterns of three phylogenetic groups of Betaproteobacteria in a coastal subtropical lagoon that is characterized by a sharp transition from humic freshwater to turbid brackish water. Various cellular processes were addressed by short-term incubations with four radiolabelled compounds and microautoradiographic assessment of substrate incorporation. Group-specific differences in the abundances and the respective physiological state of the three populations were observed upon transfer from the humic-rich compartment to the main body of the lagoon (estimated at 1-2 days).

Spatio-temporal niche separation of planktonic Betaproteobacteria in an oligo-mesotrophic lake.

We investigated the diversity of planktonic Betaproteobacteria and the seasonal population changes of betaproteobacterial taxa in an oligo-mesotrophic lake (Piburger See, Austria). Focus was put on the vertical distribution of the investigated populations and on differences between their respective cell fractions with apparent amino acid incorporation. On average, 66% of betaproteobacterial cells and 73% of their diversity could be attributed to four clades within three lineages that were further analysed by fluorescence in situ hybridization.

13C-labelling patterns of green leaf volatiles indicating different dynamics of precursors in Brassica leaves.

To investigate the dynamics of precursor compounds of green leaf volatiles (GLV)s and other biogenic compounds released by mechanically damaged Brassica oleracea leaves, plants were exposed for two consecutive 16h light phases to highly enriched (13)CO(2). Analysis by GC-MS indicated (1) biogenic compounds released upon wounding, (2) a different labelling pattern between and (3) within compounds, and (4) evidence for spatial heterogeneity of the precursor pool extrapolated from points (1)-(3). First, GLVs comprised C(5) and C(6) molecules, with the GLV pentenyl acetate being reported here for the first time from higher plants.