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: Fungal spores constitute the most abundant fraction of biological aerosols in the atmosphere, influencing human health, the biosphere, atmospheric chemistry, and climate. However, the total abundance of fungal spores in the atmosphere is rather uncertain and likely underestimated to a large extent by traditional Colony Forming Units (CFU) assays. In this study, flow cytometry (FCM) was utilized in combination with fluorescent stains for the rapid counting of ambient fungal spores, with complementary quantification of two molecular tracers for fungal spores. The FCM results had significant positive correlation with the concentrations of the fungal tracers (R2 was 0.75 and 0.70 for arabitol and mannitol, respectively). During this study, total particle counts, fungal spore numbers and the fractions of fungal spores of the total particle numbers were in the range of 44,698–9,54,211 m−3, 8224–261,154 m−3 and 1.9–46.5%, respectively, at an urban location in northern China. Meteorological conditions were shown to have complex effects on the ambient concentrations of fungal spores: the number concentrations of fungal spores exhibited significant positive correlation with relative humidity and temperature, negative correlation with wind speed and no relationship with solar radiation during the sampling period.Journal of Aerosol Science 12/2013; 66:179–186. DOI:10.1016/j.jaerosci.2013.08.013 · 2.71 Impact Factor
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ABSTRACT: Recent experiments to fossilize microorganisms using silica have shown that the fossilization process is far more complex than originally thought; microorganisms not only play an active role in silica precipitation but may also remain alive while silica is precipitating on their cell wall. To better understand the mechanisms that lead to the preservation of fossilized microbes in recent and ancient rocks, we experimentally silicified a Gram-positive bacterium, Geobacillus SP7A, over a period of five years. The microbial response to experimental fossilization was monitored with the use of LIVE/DEAD staining to assess the structural integrity of the cells during fossilization. It documented the crucial role of silicification on the preservation of the cells and of their structural integrity after several years. Electron microscopy observations showed that initial fossilization of Gram-positive bacteria was extremely rapid, thus allowing very good preservation of Geobacillus SP7A cells. A thick layer of silica was deposited on the outer surface of cell walls in the earliest phase of silicification before invading the cytoplasmic space. Eventually, the cell wall was the only recognizable feature. Heavily mineralized cells thus showed morphological similarities with natural microfossils found in the rock record.Geomicrobiology 01/2013; 31(7). DOI:10.1080/01490451.2013.860208 · 1.80 Impact Factor
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ABSTRACT: Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapment procedures are known to affect the viability of bacterial cells. To determine the effect of entrapment procedures on viability of bacterial cells, dissolution of the entrapment matrices using chelating agents or heat is required immediately after the entrapment is completed. Chelating agents and heat applied in the matrix dissolution reduce cell viability and in turn hinder accurate quantification of viable cells. In this study, a method to determine the effect of entrapment procedure on bacterial cell viability which involves entrapping cells directly onto glass slides was developed. The developed method showed less viability reduction than the methods requiring matrix dissolution. The percentage of live cells in the culture before entrapment ranged from 54% to 74%, while the percent of live cells after entrapment determined by the developed method was 39-62%.Bioresource Technology 09/2010; 102(2):1622-7. DOI:10.1016/j.biortech.2010.09.027 · 5.04 Impact Factor