Water Microbiota Research Articles

Surviving the Snowball

GEOLOGY Before the pre-Cambrian-Cambrian boundary, there is geological evidence of periods of extraordinarily extreme climatic variation. Some postulate this veered from millions of years of total glaciation at −50°C to sudden shifts to surface temperatures averaging 40°C. The exact nature of the physical conditions is hotly debated, as are the effects of these extremes on the survival of prevailing life forms. In their examination of the microfossils of Death Valley, Corsetti et al. have found complex communities of prokaryotes and eukaryotes preserved in cherts and carbonate rocks, including various forms of stromalites and oncoids. The communities seen in the preglacial cherts are very similar to those in the postglacial carbonate films, and it appears that complex communities persisted for 200 million years of climatic vacillation. The new findings suggest that the environmental scars noted in the geological record were not so severe that mass extinction of shallow water microbiota occurred, at least in shallow tropical seas.— CA Proc. Natl. Acad. Sci. U.S.A. 100 , 4399 (2003).

Monitoring of the evolving diversity of the microbial community present in rotifer cultures

The genetic fingerprint of the microbiota in the culture water of two different rotifer culture systems (batch versus recirculation) was obtained by means of denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The genetic profile of the bacterial community present in the culture water of a batch culture system changed daily due to shifts occurring at the level of the dominance of bands. By means of statistical tools, it was possible to distinguish three different periods during the development of the microbiota in the recirculation experiment, each corresponding to a typical period during the production of rotifers. Overall, it was obvious that the microbiota in such a recirculation system was less susceptible for variation relative to the microbiota in a batch system. However, some shifts in the genetic profile were observed when technical problems occurred resulting in a reduced water quality or performance of the biofilter. Characterisation of the microbial community present in the recirculation system indicated that the sequences of typical bands showed the highest level of identity to the sequences from the bacterial strain MMB-1 T (representing a species in the genus Marinomonas, Marinomonas mediterranea sp.), M. vaga and Pseudoalteromonas haloplanktis spp. tetraodonis strain IAM 14160 (98%).

Numerical analysis of planktonic and reed biofilm bacterial communities of Lake Fertő (Neusiedlersee, Hungary/Austria)

Although heterotrophic bacterial populations are of utmost importance in the self-purification and detoxification processes of aquatic ecosystems, there are insufficient data available on the composition and activities of these microbial communities. Due to these facts water bacteriological studies concentrate more on the detailed species level analyses of complex bacterial communities. At the same time by investigating many biochemical properties of the strains, one can get information on their possible activities and interrelations. In order to have a more complete understanding of bacteria living in the Neusiedlersee (Lake Fertő), a shallow, turbid, mesotrophic lake, 296 bacterial strains were subjected to morphological and detailed physiological–biochemical studies. They were determined at least at generic level. The predominant members of the bacterioplankton were aerobic respiratory organisms. A great number of the isolated strains could tolerate high salt concentrations, grew at high pH values and were mostly inactive in their degradation capabilities. A wide variety of taxa proved to be present in open waters, the predominant ones, the members of the genera Micrococcus, Pseudomonas and the Flavobacterium-Cytophaga group were almost in equal proportions. The distribution of bacteria widely varied among sampling regions. Compared with the Lake Balaton, where cocci dominate in the open water microbiota, the continuous presence of Gram-negative rods refers here to the continuous relatively high suspended solids content of the water. The reed epiphytic bacterial communities seem to be less diverse at species level and coryneforms seem to be in dominant position. Open water species diversity seems to be depended on the suspended solid content, whereas on the contrary in reed biofilms lower suspended solid values help to build up higher species diversity.

Microbiota in the drinking water: “Pseudocon-tamination” of a hospital water supply

Microbiota in the drinking water: “Pseudocon-tamination” of a hospital water supply