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: The effect of water depth on bacterial biomass and their ability to sy nthesisc DNA. by measuring their rate of ("I- thymidine incorporation, was investigated in the northeast Atlantic at three sites of varying waLer depth (1 100-3580 m) and sediment characteristics. Thymidine incorporation rates Cy) in surficial sediments varied between 0.028 and 1.44 pmol h-' g-' and showed an exponential relationship with depth (x) according to the equation y = 2,05e-0.~0~ x (r=0.9830 for n=7, PcO.OU 1). However, this relationship failed when a layer of phy todetritus was found overlying the sucfacc scdirnent and (3 HI-thymidine incorporation rates increased by 8s339'90. In contrast, baclerial numhers varied between 1.09 and 1 1.96 x 10%lls llsg' (dry weight) and showed no significant re- lationships with water depth or scdiment POmN content. Significant exponential rcla~ionships werc also found between walcr depth (x) and the POT: Cy 1) and totsll nitrogen (TN, yz) content of suficial sediments according to the following equations: where yl = 7 19c-.0,0DO'X (rd.8700 for n=9, f ~0.01) and yz = 76eL0.0002"(r=0.7582 for n=9 Pt0.02). These relationships were irrespective of the presence or absence of an overlying layer of phytodetritus. This suggests that the POC and TN cantent of these surficial deep sea sediments is dircctly rclaied to the flux of malerial though the water column, which significantly impacts bacterial produc~ian.Hydrobiologia 12/2000; 440(1-3). · 1.99 Impact Factor
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ABSTRACT: Viable but non-culturable (VBNC) bacteria are a much discussed issue in microbial ecology. Quantitative aspects are not understood, due mostly to the lack of suitable techniques. A widely accepted approach is dependent on the integrity of cell membranes. Recently developed fluorescence dyes differ in permeability with respect to the integrity of membranes: one dye permeates the intact membranes, which another permeates those which are damaged. Although the dyes were developed originally for determining the viability of cultured bacteria, here they are used to enumerate live and dead bacterial cells (designated as having intact and damaged membranes, respectively) in natural environments. Preliminary results from coastal waters of Seto Inland Sea, Japan, were: 1) the sums of the intact and damaged cells were very similar in each case to the total number of acridine orange-stained cells; and 2) about 50–60% of the total bacteriaoplankton populations are intact with respect to membrane integrity.Journal of Aquatic Ecosystem Stress and Recovery 10/1996; 5(4):217-222.
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ABSTRACT: In the Arabian Sea, productivity in the surface waters and particle flux to the deep sea are controlled by monsoonal winds. The flux maxima during the South-West (June–September) and the North-East Monsoon (December–March) are some of the highest particle fluxes recorded with deep-sea sediment traps in the open ocean. Benthic microbial biomass and activities in surface sediments were measured for the first time in March 1995 subsequent to the NE-monsoon and in October 1995 subsequent to the SW-monsoon. These measurements were repeated in April/May 1997 and February/March 1998, at a total of six stations from 1920 to 4420 m water depth. This paper presents a summary on the regional and temporal variability of microbial biomass, production, enzyme activity, degradation of -labeled Synechococcus material as well as sulfate reduction in the northern, western, eastern, central and southern Arabian deep sea. We found a substantial regional variation in microbial biomass and activity, with highest values in the western Arabian Sea (station WAST), decreasing approximately threefold to the south (station SAST). Benthic microbial biomass and activity during the NE-monsoon was as high or higher than subsequent to the SW-monsoon, indicating a very rapid turnover of POC in the surface sediments. This variation in the biomass and activity of the microbial assemblages in the Arabian deep sea can largely be explained by the regional and temporal variation in POC flux. Compared to other abyssal regions, the substantially higher benthic microbial biomasses and activities in the Arabian Sea reflect the extremely high productivity of this tropical basin.Deep Sea Research Part II: Topical Studies in Oceanography. 01/2000;