Application of a rapid direct viable count method to deep-sea sediment bacteria
ABSTRACT For the first time, a Live/Dead (L/D) Bacterial Viability Kit (BacLight ) protocol was adapted to marine sediments and applied to deep-sea sediment samples to assess the viability (based on membrane integrity) of benthic bacterial communities. Following a transect of nine stations in the Fram Strait (Arctic Ocean), we observed a decrease of both bacterial viability and abundance with increasing water (1250-5600 m) and sediment depth (0-5 cm). Percentage of viable (and thus potentially active) cells ranged between 20-60% within the first and 10-40% within the fifth centimetre of sediment throughout the transect, esterase activity estimations (FDA) similarly varied from highest (13.3+/-5.4 nmol cm(-3) h(-1)) to lowest values below detection limit down the sediment column. Allowing for different bottom depths and vertical sediment sections, bacterial viability was significantly correlated with FDA estimations (p<0.001), indicating that viability assessed by BacLight staining is a good indicator for bacterial activity in deep-sea sediments. Comparisons between total L/D and DAPI counts not only indicated a complete bacterial cell coverage, but a better ability of BacLight staining to detect cells under low activity conditions. Time course experiments confirmed the need of a rapid method for viability measurements of deep-sea sediment bacteria, since changes in pressure and temperature conditions caused a decrease in bacterial viability of up to 50% within the first 48 h after sample retrieval. The Bacterial Viability Kit proved to be easy to handle and to provide rapid and reliable information. It's application to deep-sea samples in absence of pressure-retaining gears is very promising, as short staining exposure time is assumed to lessen profound adverse effects on bacterial metabolism due to decompression.
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ABSTRACT: Sewage sludges from wastewater treatment plants may contain live parasite eggs, which can be a source of humans and animals infection. According to the current rules, parasitological examination includes detection of the Ascaris spp., Trichuris spp. and Toxocara spp. eggs and estimation of their viability. The viability assessment based only on the incubation and observation of isolated egg is long and imprecise. The aim of this study was to develop sensitive and less labourintensive methods for assessing viability of Ascaris spp., Toxocara spp. and Trichuris spp. eggs in sewage sludge. For this purpose, LIVE/DEAD Kit was used. Firstly, the possibility of distinguishing between live and dead eggs in water was assessed. Secondly, an appropriate amount of dyeing mixture needed to distinguish the live and dead eggs in the sewage sludge was determined using experimentally enriched samples and naturally contaminated samples of sludge. Eggs were isolated from the samples by own method which was a combination of flotation and sedimentation, preceded by a long mixing. After the last stage of the procedure, sediment containing the eggs of parasites was stained by LIVE/DEAD kit according to the manufacturer instructions, but with the use of different variants of dyes mixture concentration. The investigation showed that live and dead eggs of these three parasites could be differed by this method with the use of proper concentration of dyes. Live eggs were stained in green (Ascaris and Trichuris) and green-blue (Toxocara). However, all types of dead eggs were red coloured. The study demonstrated that after some modifications (resulted from the nature of the samples) the LIVE/DEAD kit is useful for assessing the viability of Toxocara, Ascaris and Trichuris eggs occurring in the sludge.Annals of agricultural and environmental medicine: AAEM 04/2014; 21(1):35-41. · 3.06 Impact Factor
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ABSTRACT: Estimation of total bacterial counts and some physicochemical parameters in different sites selected along the Suez Bay was carried out. The highest bacterial density positively correlated with pollution strength and localized in the end of the Suez Bay on the one hand of Suez Gulf and is a function of pollution strength at the different examined sites. Antagonistic interactions among twenty two bacterial isolates dominating water were assayed. The marine isolate AB12 isolated from sea water of NIOF station displayed the highest antagonistic activity (42.8%). Antagonistic isolates were assigned to phylogenetically 4 different phena which were identified as Staphylococcus, Micrococcus, Enterococcus and Enterobacter species in addition to 5 single clusters which were identified as Acinetobacter sp., Micrococcus sp. and Pseudomonas sp. The promising strain was identified at the molecular level as Pseudoalteromonas piscicida.
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ABSTRACT: An experimental study was carried out to observe the microbial response to two different plankton-derived organic matter inputs in a coastal sedimentary community of Ubatuba, São Paulo, SE Brazil. The organic enrichment experiment was conducted in order to test experimentally the stimulus of the sediment prokaryotic community after the input of labile material simulating an algal bloom reaching the sea floor. A total of 57 corers (two treatments: the diatom Phaeodactylum tricornutun and the phytoflagelate Tetraselmis sp. and a control) were maintained for a total of 30 days in constant temperature, circulation and oxygenation. After the addition of algae an increase in oxygen consumption was observed, accompanied by an increase of prokaryotic total and live density, showing an immediate response from the community to the input of labile material in the sediment. Analyses of molecular fingerprints of bacterial communities by denaturing gel gradient electrophoresis (DGGE) showed differences in bacterial community composition between both treatments and control just after algae addition. This was well evidenced after bacteria genomic libraries analyses that showed differences in diversity and dominance between treatments. In general, Gammaproteobacteria was the most diverse and abundant group in the sediment samples. However, the addition of phytoflagellates led to a shift in dominance in favor of Alphaproteobacteria while diatom input led to a greater bacterial diversity.Journal of Experimental Marine Biology and Ecology 09/2014; 461:257-266. DOI:10.1016/j.jembe.2014.08.017 · 2.48 Impact Factor