Estimation of bacterial production in fresh waters by the simultaneous measurement of [35S]sulphate and d-[3H]glucose uptake in the dark

Contribution of particle-bound bacteria to total microheterotrophic activity in five ponds and two marshes

We examined the abundance and heterotrophic uptake of bacteria attached to particulate matter suspended in five coastal ponds and two marshes near Woods Hole, Mass. Although the number of particle-bound bacteria was low (<10%), these bacteria incorporated a large proportion (>40%) of [C]glucose and [C]glutamate in selected aquatic systems. The uptake per cell was significantly higher for epibacteria than for unattached bacteria in all systems. Two groups of the aquatic environments sampled were statistically different in the contribution made by particle-bound bacteria to total bacterial abundance and to total assimilation of [C]glucose and [C]glutamate. Particle-bound bacteria were more important in those waters with a high particle concentration and not flushed regularly by tides than in waters with a low particle concentration and flushed regularly.

Assessing biomass and production of bacteria in eutrophic lake mendota, wisconsin

Estimates were made of the biomass and production of heterotrophic bacteria in the epilimnion of Lake Mendota, Wis. Cell counts were done with epifluorescence microscopy and varied from 3 x 10 bacteria per ml in winter to 3 x 10 bacteria per ml in summer. Cell volumes were measured in scanning electron micrographs. The average cell volume was 0.159 mum. Annual variations and depth distribution were studied. Production was estimated from the frequency of dividing cells and from dark radioactive sulfate uptake. Annual productivity and daily average productivity were very close with both methods: 107 to 205 g of C per m per year for sulfate and 89 to 117 g of C per m per year for frequency of dividing cells. Zooplankton feeding removed 2 to 10% of the bacterial net production annually. When compared with biomass changes and losses due to zooplankton feeding, production values were very high. Therefore, it was suggested that other loss factors have to be more important than zooplankton feeding in controlling the bacterial population. Bacterial heterotrophic production was about 50% of gross primary production.

Seasonal variation in population density and heterotrophic activity of attached and free-living bacteria in coastal waters

The abundance and heterotrophic activity of attached and free-living bacteria were examined seasonally in coastal water. Heterotrophic activity was determined by the uptake of [C]glucose. The density of attached bacteria was always minor, not showing a seasonal variation, whereas the free-living bacteria were more numerous and showed a marked seasonal variation, their density being higher under warmer conditions. The contribution of the attached bacteria to the total assimilation of [C]glucose (from 10 to 38%) was lower than that of the free-living bacteria, neither of them showing a seasonal variation. On a cellular basis, attached bacteria were more active, since they assimilated more [C]glucose and showed, under warmer conditions, a higher cellular volume (0.102 versus 0.047 mum). We consider that the factors responsible for these observations were the amount and quality of the particulate material, the different availability of organic matter for the two types of bacteria, and in a fundamental way, the variation in water temperature.

Assimilatory Sulfur Metabolism in Marine Microorganisms: Sulfur Metabolism, Protein Synthesis, and Growth of Alteromonas luteo-violaceus and Pseudomonas halodurans During Perturbed Batch Growth

The antibiotic protein synthesis inhibitor chloramphenicol specifically blocked the incorporation of [S]sulfate into the residue protein of two marine bacteria, Pseudomonas halodurans and Alteromonas luteo-violaceus. Simultaneous inhibition of total protein synthesis occurred, but incorporation of S into low-molecular-weight organic compounds continued. A. luteo-violaceus rapidly autolyzed, with similar reduction in cell counts, total culture protein and cellular sulfur, whereas P. halodurans remained viable. Treatment with chloramphenicol, growth during nitrogen and carbon limitation, and the carbon and energy sources used for growth did not alter the sulfur content of P. halodurans protein. The mean value (1.09%, by weight), representing a wide variety of environmentally relevant growth conditions, was in agreement with model protein composition. The variability of cellular composition of P. halodurans and A. luteo-violaceus is discussed with respect to the measurement of bacterial growth in natural environments. Total carbon and nitrogen per cell varied greatly (coefficient of variation, ca. 100%) depending on growth conditions. Variation in total sulfur and protein per cell was much less (coefficient of variation, <50%), but the least variation was found for sulfate incorporation into residue protein (coefficient of variation, ca. 15%). Thus, sulfate incorporation into residue protein can be used as an accurate measurement of de novo protein synthesis in these bacteria.