Sylwia Lew

Selected fluorescent techniques for identification of the physiological state of individual water and soil bacterial cells — review

Stimulated by demands of the natural environment conservation, the need for thorough structural and functional identification of microorganisms colonizing different ecosystems has contributed to an intensive advance in research techniques. The article shows that some of these techniques are also a convenient tool for determination of the physiological state of single cells in a community of microorganisms. The paper presents selected fluorescent techniques, which are used in research on soil, water and sediment microorganisms. It covers the usability of determination of the dehydrogenase activity of an individual bacterial cell (CTC+) and of bacteria with intact, functioning cytoplasmic membranes, bacteria with an integrated nucleiod (NuCC+) as well as fluorescent in situ hybridization (FISH).

Effects of lateral connectivity on zooplankton community structure in floodplain lakes

Hydrological conditions are responsible for the changes in lateral connectivity between the main river channel and the floodplain lakes, a factor controlling zooplankton abundance and diversity. We tested the hypothesis that the degree of connectivity between the aquatic habitats and the river channel governs the zooplankton densities and community structure. Abundances, community composition and species diversity of zooplankton were analysed against the gradient of lakes’ connectivity and the water quality parameters under a natural flood pulse in the Biebrza River (North-Eastern Poland). Our findings revealed that the water level fluctuations directly affect the availability of nutrients, aeration, what in turn controls the densities and biovolumes of zooplankton communities. Along with the increase in the lake isolation, the taxonomic diversity of zooplankton decreased, while the eudomination of taxa indicative of advanced trophy (Rotifera) was observed. Qualitative parameters, as number of species, diversity and richness, were significantly higher at mean water levels, which supports the intermediate disturbance hypothesis. The sensitivity of the zooplankton community to variable hydrological conditions and lateral connectivity gradient demonstrates its potential as an unexploited indicator of any habitat changes in the aquatic ecosystems.

Environmental controls on the abundance of methanotrophs and methanogens in peat bog lakes

The aim of the present study was to identify the factors that influence the composition of methanogens and methanotrophs in the background prokaryotic community in peat bog lakes. We hypothesized that the microbial composition is a function of the physicochemical conditions of the water and a function of depth-dependent oxygen (DO) concentrations. To address this aim, we collected water samples from subsurface and near-bottom layers, representing oxic and anoxic conditions in 4 peat bog lakes in NE Poland. The structure of methanogenic Archaea and methane-oxidizing bacteria (MOB) was determined with double labeled-fluorescence in situ hybridization (DOPE-FISH). The results showed significant differences in Procaryota communities between the oxic (subsurface) and suboxic/anoxic (near-bottom) layers in peat bog lakes (t-test, p < 0.05). The methanogens from the Archaea domain were observed in anoxic periods, while methanotrophs were present regardless of water depth and season. The abundance of methanogens was inversely correlated with DO and CO2. Methanotrophs adapted better to the changing habitat conditions. The nonmetrical multidimensional scaling (NMS) and partial least square regression (PLS-R) models showed that the methanotrophs in subsurface layers are positively associated with temperature, DOC, and TON while negatively associated with pH. The DO availability is not a prerequisite condition for the presence of methanothrophs. The most important factors for MOB at the bottom were CO2 and TON. Due to a significant role of methanotrophs in the control of the methane emission flux rates, there is a need for further research on factors responsible for methanotroph development in peat bog lakes.

Electroretinographic findings in day-blind dogs

Cone degeneration (cd; day blindness) is one of the inherited retinal diseases of dogs. Its diagnosis is based on vision testing, fundoscopy, electroretinography (ERG) and, for some breeds, on genetic tests. Typical signs of the disease are day blindness and cone dysfunction during ERG while fundoscopy does not show any abnormalities. The aim of this study was to compare behavioural findings, fundoscopic lesions and electroretinographic alterations in 12 cd-affected dogs (Alaskan Malamute, Labrador Retriever, German Shepherd, Dachshund, Yorkshire Terrier, Shih Tzu, Siberian Husky and crossbreeds) examined at our clinic. None of the examined dogs had any fundoscopic lesions, and all of them had normal scotopic vision with strongly impaired or absent photopic vision. Light-adapted transient, cone-mediated and steady-state, 31-Hz cone flicker ERGs were much below the 5th percentile limits of normality or even unrecordable, while the rod-driven ERGs were within normal values. Vision test and ERG results corresponded to each other and, combined with the results of fundoscopy, were typical of cd. To date, our research is one of the few studies in the world presenting ERG alterations compared with vision test findings and fundoscopic results in the course of cd.