Activity of an Attached and Free-Living Vibrio sp. as Measured by Thymidine Incorporation, p -Iodonitrotetrazolium Reduction, and ATP/DNA Ratios

Salinity and seasonality shaping free-living and particle-associated bacterioplankton community assembly in lakeshores of the northeastern Qinghai-Tibet Plateau

Microorganisms in lakeshore zones are essential for pollution interception and biodiversity maintenance. However, the biogeographic patterns of bacterioplankton communities in lakeshore zones and the mechanisms that driving them are poorly understood. We analyzed the 16 S rRNA gene sequences of particle-associated (PA) and free-living (FL) bacterioplankton communities in the lakeshore zones of 14 alpine lakes in two seasons on Qinghai-Tibet Plateau to investigate the bacterial diversity, composition and assembly processes. Our results revealed that PA and FL bacterioplankton communities were driven by both seasonality and salinity in the lakeshores on Qinghai-Tibet Plateau. Compared to FL bacterioplankton, PA bacterioplankton communities were more susceptible to seasonality than spatial salinity. FL bacterioplankton communities were more salinity constrained than the PA counterpart. Besides, the Stegen null model analyses have validated a quantitative bias on stochastic processes at different spatial scales. At a regional scale, stochasticity was the predominant assembly process in both PA and FL bacterioplankton. While at a subregional scale, dispersal limitation was the main contributor of stochastic processes for PA bacterioplankton in summer and heterogeneous selection was the dominant deterministic processes in winter, whereas the community assembly of FL bacterioplankton was more stochastic processes (i.e., dispersal limitation) dominated in the freshwater type but deterministic process (i.e., heterogeneous selection) increased with increasing salinity. Our study provides new insights into both significant spatiotemporal patterns and distinct assembly processes of PA and FL bacterioplankton in alpine lakeshores on the northeastern Qinghai-Tibet Plateau.

Investigating and Modeling the Regulation of Extracellular Antibiotic Resistance Gene Bioavailability by Naturally Occurring Nanoparticles

Extracellular antibiotic resistance genes (eARGs) are widespread in the environment and can genetically transform bacteria. This work examined the role of environmentally relevant nanoparticles (NPs) in regulating eARG bioavailability. eARGs extracted from antibiotic-resistant B. subtilis were incubated with nonresistant recipient B. subtilis cells. In the mixture, particle type (either humic acid coated nanoparticles (HASNPs) or their micron-sized counterpart (HASPs)), DNase I concentration, and eARG type were systematically varied. Transformants were counted on selective media. Particles decreased bacterial growth and eARG bioavailability in systems without nuclease. When DNase I was present (≥5 μg/mL), particles increased transformation via chromosomal (but not plasmid-borne) eARGs. HASNPs increased transformation more than HASPs, indicating that the smaller nanoparticle with greater surface area per volume is more effective in increasing eARG bioavailability. These results were also modeled via particle aggregation theory, which represented eARG-bacteria interactions as transport leading to collision, followed by attachment. Using attachment efficiency as a fitting factor, the model predicted transformant concentrations within 35% of experimental data. These results confirm the ability of NPs to increase eARG bioavailability and suggest that particle aggregation theory may be a simplified and suitable framework to broadly predict eARG uptake.

The Partial Contribution of Constructed Wetland Components (Roots, Gravel, Microorganisms) in the Removal of Phenols: A Mini Review

Constructed wetlands (CW) have attracted growing interest in wastewater treatment research in the last 20 years, and have been investigated intensively worldwide. Many of the basic processes occurring in CWs have been qualitatively established; however, much quantitative knowledge is still lacking. In this mini review, the proportionate contributions of the different system components to removal of contaminants are examined. The main objective of this mini review is to provide a more in-depth assessment of the interactions between the porous bed, plants, and microorganisms during the removal of organic contaminants from the water in a subsurface flow CW system. In addition, a unique technique to study the partial contribution to the total removal of contaminants in a CW is described. Future studies in this field will expand our knowledge of any synergistic or antagonistic interactions between the components and facilitate improved CW construction and operation. Here, phenol will be used as a model industrial organic contaminant to illustrate our current understanding of the contributions of the different components to total removal. I will also discuss the various factors influencing the efficacy of bacteria, whether planktonic or as biofilm (on porous bed or plant roots), in subsurface flow CWs.

Kinetics and inhibition of reductive dechlorination of trichloroethene, cis-1,2-dichloroethene and vinyl chloride in a continuously fed anaerobic biofilm reactor

Anaerobic bioreactors containing Dehalococcoides spp. can be effective for the treatment of trichloroethene (TCE) contamination. However, reductive dehalogenation of TCE often results in partial conversion to harmless ethene, and significant production of undesired cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) is frequently observed. Here, a detailed modeling study was conducted focusing on the determination of biokinetic constants for the dechlorination of TCE and its reductive dechlorination intermediates cis-DCE and VC as well as any biokinetic inhibition that may exist between these compounds. Dechlorination data from an anaerobic biotrickling filter containing Dehalococcoides spp. fed with single compounds (TCE, cis-DCE, or VC) were fitted to the model to determine biokinetic constants. Experiments with multiple compounds were used to determine inhibition between the compounds. It was found that the Michaelis-Menten half-saturation constants for all compounds were higher than for cells grown in suspended cultures, indicating a lower enzyme affinity in biofilm cells. It was also observed that TCE competitively inhibited the dechlorination of cis-DCE and had a mild detrimental effect on the dechlorination of VC. Thus, careful selection of biotreatment conditions, possibly with the help of a model such as the one presented herein, is required to minimize the production of partially dechlorinated intermediates.

Efficiency of phenol biodegradation by planktonic Pseudomonas pseudoalcaligenes (a constructed wetland isolate) vs. root and gravel biofilm

In the last two decades, constructed wetland systems gained increasing interest in wastewater treatment and as such have been intensively studied around the world. While most of the studies showed excellent removal of various pollutants, the exact contribution, in kinetic terms, of its particular components (such as: root, gravel and water) combined with bacteria is almost nonexistent. In the present study, a phenol degrader bacterium identified as Pseudomonas pseudoalcaligenes was isolated from a constructed wetland, and used in an experimental set-up containing: plants and gravel. Phenol removal rate by planktonic and biofilm bacteria (on sterile Zea mays roots and gravel surfaces) was studied. Specific phenol removal rates revealed significant advantage of planktonic cells (1.04 × 10(-9) mg phenol/CFU/h) compared to root and gravel biofilms: 4.59 × 10(-11)-2.04 × 10(-10) and 8.04 × 10(-11)-4.39 × 10(-10) (mg phenol/CFU/h), respectively. In batch cultures, phenol biodegradation kinetic parameters were determined by biomass growth rates and phenol removal as a function of time. Based on Haldane equation, kinetic constants such as μ(max) = 1.15/h, K(s) = 35.4 mg/L and K(i) = 198.6 mg/L fit well phenol removal by P. pseudoalcaligenes. Although P. pseudoalcaligenes planktonic cells showed the highest phenol removal rate, in constructed wetland systems and especially in those with sub-surface flow, it is expected that surface associated microorganisms (biofilms) will provide a much higher contribution in phenol and other organics removal, due to greater bacterial biomass. Factors affecting the performance of planktonic vs. biofilm bacteria in sub-surface flow constructed wetlands are further discussed.

Stimulation of bacterial DNA synthesis by algal exudates in attached algal-bacterial consortia

Algal-bacterial consortia attached to polystyrene surfaces were prepared in the laboratory by using the marine diatom Amphora coffeaeformis and the marine bacterium Vibrio proteolytica (the approved name of this bacterium is Vibrio proteolyticus [W. E. C. Moore, E. P. Cato, and L. V. H. Moore, Int. J. Syst. Bacteriol. 35:382-407, 1985]). The organisms were attached to the surfaces at cell densities of approximately 5 x 10 cells cm (diatoms) and 5 x 10 cells cm (bacteria). The algal-bacterial consortia consistently exhibited higher rates of [H]thymidine incorporation than did biofilms composed solely of bacteria. The rates of [H]thymidine incorporation by the algal-bacterial consortia were fourfold greater than the rates of incorporation by monobacterial biofilms 16 h after biofilm formation and were 16-fold greater 70 h after biofilm formation. Extracellular material released from the attached Amphora cells supported rates of bacterial activity (0.8 x 10 to 17.9 x 10 mol of [H]thymidine incorporated cell h) and growth (doubling time, 29.5 to 1.4 days) comparable to values reported for a wide variety of marine and freshwater ecosystems. In the presence of sessile diatom populations, DNA synthesis by attached V. proteolytica cells was light dependent and increased with increasing algal abundance. The metabolic activity of diatoms thus appears to be the rate-limiting process in biofilm development on illuminated surfaces under conditions of low bulk-water dissolved organic carbon.

Activity measurements of planktonic microbial and microfouling communities in a eutrophic estuary

[H]thymidine incorporation, the rate of reduction of iodonitrotetrazolium violet (INT) to INT formazan normalized to DNA, and the ratio of ATP to DNA were adapted to measure the activity of attached and unattached microbial assemblages of Bayboro Harbor, Fla. Activity measurements by [H]thymidine incorporation were made of cells attached to polystyrene culture dishes, in unfiltered water samples, and in the <1-mum-filtered fraction. In most cases, the activity of attached cells was greater than that of unattached cells either in unfiltered water samples or in the <1-mum fraction. The calculated thymidine incorporation rates for cells in the >1-mum fraction were higher than those for cells either in unfiltered water or in the <1-mum-filtered fraction. By the rate of reduction of INT to INT formazan normalized to DNA and by ATP-to-DNA ratios, attached cells were also more active than cells in unfiltered water samples. These results indicate that the microenvironment afforded by attachment is a more beneficial habitat for microbial growth. Reasons for greater activity by natural populations of attached bacteria are discussed.

Effect of 5-fluoro-2'-deoxyuridine on [h]thymidine incorporation by bacterioplankton in the waters of southwest Florida

The effect of 5-fluoro-2'-deoxyuridine (FdUrd) on [methyl-H] thymidine incorporation by bacterioplankton populations in subtropical freshwater, estuarine, and oceanic environments was examined. In estuarine waters, intracellular isotope dilution was inhibited by FdUrd, which enabled us to estimate both intracellular and extracellular isotope dilution. In 2 of 10 cases, extracellular isotope dilution was significant. At low concentrations of [methyl-H]thymidine or [6-H]thymidine, FdUrd completely inhibited incorporation of radioactivity into protein and RNA. At high concentrations of [H]thymidine, however, FdUrd had little effect on labeling patterns. The dihydrofolate reductase inhibitors amethopterin and trimethoprim had no effect on macromolecular labeling patterns. These results suggest that thymidylate synthase is not involved in nonspecific labeling and that FdUrd inhibits nonspecific labeling by blocking some other enzyme involved in thymidine catabolism. In oligotrophic oceanic and freshwater samples, FdUrd did not inhibit intracellular isotope dilution or [H]thymidine labeling of protein and RNA, but caused some inhibition of [H]thymidine incorporation into DNA. The ability of FdUrd to inhibit nonspecific macromolecular labeling during [H]thymidine incorporation was significantly correlated (r = 0.84) with total thymidine incorporation (in picomoles per liter per hour). The results are discussed in terms of applications of FdUrd to routine bacterial production measurements and the general assumptions of [H]thymidine incorporation.

Underestimation of DNA synthesis by [h]thymidine incorporation in marine bacteria

A direct comparison of [H]thymidine incorporation with DNA synthesis was made by using an exponentially growing estuarine bacterial isolate and the naturally occurring bacterial populations in a eutrophic subtropical estuary and in oligotrophic offshore waters. Simultaneous measurements of [H]thymidine incorporation into DNA, fluorometrically determined DNA content, and direct counts were made over time. DNA synthesis estimated from thymidine incorporation values was compared with fluorometrically determined changes in DNA content. Even after isotope dilution, nonspecific macromolecular labeling, and efficiency of DNA recovery were accounted for, [H]thymidine incorporation consistently underestimated DNA synthesized by six- to eightfold. These results indicate that although the relationship of [H]thymidine incorporation to DNA synthesis appears consistent, there are significant sources of thymine bases incorporated into DNA which cannot be accounted for by standard [H]thymidine incorporation and isotope dilution assays.

Cell immobilization for production of lactic acid biofilms do it naturally

Interest in natural cell immobilization or biofilms for lactic acid fermentation has developed considerably over the last few decades. Many studies report the benefits associated with biofilms as industrial methods for food production and for wastewater treatment, since the formation represents a protective means of microbial growth offering survival advantages to cells in toxic environments. The formation of biofilms is a natural process in which microbial cells adsorb to a support without chemicals or polymers that entrap the cells and is dependent on the reactor environment, microorganism, and characteristics of the support. These unique characteristics enable biofilms to cause chronic infections, disease, food spoilage, and devastating effects as in microbial corrosion. Their distinct resistance to toxicity, high biomass potential, and improved stability over cells in suspension make biofilms a good tool for improving the industrial economics of biological lactic acid production. Lactic acid bacteria and specific filamentous fungi are the main sources of biological lactic acid. Over the past two decades, studies have focused on improving the lactic acid volumetric productivity through reactor design development, new support materials, and improvements in microbial production strains. To illustrate the operational designs applied to the natural immobilization of lactic acid producing microorganisms, this chapter presents the results of a search for optimum parameters and how they are affected by the physical, chemical, and biological variables of the process. We will place particular emphasis upon the relationship between lactic acid productivity attained by various types of reactors, supports, media formulations, and lactic acid producing microorganisms.

Toluene degradation kinetics for planktonic and biofilm-grown cells of Pseudomonas putida 54G

Toluene degradation kinetics by biofilm and planktonic cells of Pseudomonas putida 54G were compared in this study. Batch degradation of (14)C toluene was used to evaluate kinetic parameters for planktonic cells. The kinetic parameters determined for toluene degradation were: specific growth rate, micro(max) = 10.08 +/- 1.2/day; half-saturation constant, K(S) = 3.98 +/- 1.28 mg/L; substrate inhibition constant, K(I) = 42.78 +/- 3.87 mg/L. Biofilm cells, grown on ceramic rings in vapor phase bioreactors, were removed and suspended in batch cultures to calculate (14)C toluene degradation rates. Specific activities measured for planktonic and biofilm cells were similar based on toluene degrading cells and total biomass. Long-term toluene exposure reduced specific activities that were based on total biomass for both biofilm and planktonic cells. These results suggest that long-term toluene exposure caused a large portion of the biomass to become inactive, even though the biofilm was not substrate limited. Conversely, specific activities based on numbers of toluene-culturable cells were comparable for both biofilm and planktonically grown cultures. Planktonic cell kinetics are often used in bioreactor models to model substrate degradation and growth of bacteria in biofilms, a procedure we found to be appropriate for this organism. For superior bioreactor design, however, changes in cellular activity that occur during biofilm development should be investigated under conditions relevant to reactor operation before predictive models for bioreactor systems are developed.

Comparison of planktonic and biofilm cultures of Pseudomonas fluorescens DSM 8341 cells grown on fluoroacetate

Comparisons between the physiological properties of Pseudomonas fluorescens biofilm cells grown in a tubular biofilm reactor and planktonic cells grown in a chemostat were performed. Fluoroacetate was the sole carbon source for all experiments. The performance of cells was assessed using cell cycle kinetics and by determining specific fluoroacetate utilization rates. Cell cycle kinetics were studied by flow cytometry in conjunction with the fluorescent stain propidium iodide. Determination of the DNA content of planktonic and biofilm cultures showed little difference between the two modes of growth. Cultures with comparable specific glycolate utilization rates had similar percentages of cells in the B phase of the cell cycle, indicating similar growth rates. Specific fluoroacetate utilization rates showed the performance of planktonic cells to be superior to that of biofilm cells, with more fluoroacetate utilized per cell at similar specific fluoroacetate loading rates. A consequence of this decreased biofilm performance was the accumulation of glycolate in the effluent of biofilm cultures. This accumulation of glycolate was not observed in the effluent of planktonic cultures. Spatial stratification of oxygen within the biofilm was identified as a possible explanation for the overflow metabolism of glycolate and the decreased performance of the biofilm cells.

Effects of nutrients on biofilm formation and detachment of a Pseudomonas putida strain isolated from a paper machine

The aim of this study was to determine the effect of varying nutrient conditions on biofilm formation of a Pseudomonas putida strain isolated from a paper machine under controlled conditions. Biofilm accumulation, was investigated using a laminar flow cell reactor in a defined mineral medium. Our results indicate that increasing nutrient concentration (from 0.1 to 0.5 gl(-1) glucose, C/N=40, C/P=100) or phosphate concentration (from C/P=200 to C/P=100) increased the rate and extent of biofilm accumulation, however, higher nutrient (1 gl(-1) glucose, C/N=40, C/P=100) or phosphate (C/P=50) concentration reduced biofilm accumulation rate because of a higher detachment. The rate and extent of biofilm accumulation increased with nitrogen concentration (from C/N=90 to C/N=20). Detachment is a key parameter that influences biofilm accumulation since the early stage (2h) of colonisation and strongly depends on nutrient conditions. In practice, controlling nutrient levels may be interesting to reduce biofilm formation in the paper industry.

Interaction of Klebsiella oxytoca and Burkholderia cepacia in dual-species batch cultures and biofilms as a function of growth rate and substrate concentration

Dual-species microbial interactions have been extensively reported for batch and continuous culture environments. However, little research has been performed on dual-species interaction in a biofilm. This research examined the effects of growth rate and substrate concentration on dual-species population densities in batch and biofilm reactors. In addition, the feasibility of using batch reactor kinetics to describe dual-species biofilm interactions was explored. The scope of the research was directed toward creating a dual-species biofilm for the biodegradation of trichloroethylene, but the findings are a significant contribution to the study of dual-species interactions in general. The two bacterial species used were Burkholderia cepacia PR1-pTOM(31c), an aerobic organism capable of constitutively mineralizing trichloroethylene (TCE), and Klebsiella oxytoca, a highly mucoid, facultative anaerobic organism. The substrate concentrations used were different dilutions of a nutrient-rich medium resulting in dissolved organic carbon (DOC) concentrations on the order of 30, 70, and 700 mg/L. Presented herein are single- and dual-species population densities and growth rates for these two organisms grown in batch and continuous-flow biofilm reactors. In batch reactors, planktonic growth rates predicted dual-species planktonic species dominance, with the faster-growing organism (K. oxytoca) outcompeting the slower-growing organism (B. cepacia). In a dual-species biofilm, however, dual-species planktonic growth rates did not predict which organism would have the higher dual-species biofilm population density. The relative fraction of each organism in a dual-species biofilm did correlate with substrate concentration, with B. cepacia having a greater proportional density in the dual-species culture with K. oxytoca at low (30 and 70 mg/L DOC) substrate concentrations and K. oxytoca having a greater dual-species population density at a high (700 mg/L DOC) substrate concentration. Results from this research demonstrate the effectiveness of using substrate concentration to control population density in this dual-species biofilm.

Influence of substrate diffusion on degradation of dibenzofuran and 3-chlorodibenzofuran by attached and suspended bacteria

Dibenzofuran uptake-associated kinetic parameters of suspended and attached Sphingomonas sp. strain HH19k cells were compared. The suspended cells were studied in a batch system, whereas glass beads in percolated columns were used as the solid support for attached cells. The maximum specific activities of cells in the two systems were the same. The apparent half-maximum uptake rate-associated concentrations (Kt') of attached cells, however, were considerably greater than those of suspended cells and depended on cell density and on percolation velocity. A mathematical model was developed to explain the observed differences in terms of substrate transport to the cells. This model was based on the assumptions that the intrinsic half-maximum uptake rate-associated concentration (Kt) was unchanged and that deviations of Kt' from Kt resulted from the stereometry and the hydrodynamics around the cells. Our calculations showed that (i) diffusion to suspended cells and to single attached cells is efficient and therefore only slightly affects Kt'; (ii) diffusion to cells located on crowded surfaces is considerably lower than that to single attached cells and greatly increases Kt', which depends on the cell density; (iii) the convective-diffusive transport to attached cells that occurs in a percolated column is influenced by the liquid flow and results in dependency of Kt' on the flow rate; and (iv) higher specific affinity of cells correlates with higher susceptibility to diffusion limitation. Properties of the experimental system which limited quantitative proof of exclusively transport-controlled variations of Kt' are discussed.

Effect of treated-sewage contamination upon bacterial energy charge, adenine nucleotides, and DNA content in a sandy aquifer on Cape Cod

Changes in adenylate energy charge (ECA) and in total adenine nucleotides (A(T) and DNA content (both normalized to the abundance of free-living, groundwater bacteria) in response to carbon loading were determined for a laboratory-grown culture and for a contaminated aquifer. The latter study involved a 3-km-long transect through a contaminant plume resulting from continued on-land discharge of secondary sewage to a shallow, sandy aquifer on Cape Cod, Mass. With the exception of the most contaminated groundwater immediately downgradient from the contaminant source, DNA and adenylate levels correlated strongly with bacterial abundance and decreased exponentially with increasing distance downgradient. ECAS (0.53 to 0.60) and the ratios of ATP to DNA (0.001 to 0.003) were consistently low, suggesting that the unattached bacteria in this groundwater study are metabolically stressed, despite any eutrophication that might have occurred. Elevated ECAS (up to 0.74) were observed in glucose-amended groundwater, confirming that the metabolic state of this microbial community could be altered. In general, per-bacterium DNA and ATP contents were approximately twofold higher in the plume than in surrounding groundwater, although ECA and per-bacterium levels of A(T) differed little in the plume and the surrounding uncontaminated groundwater. However, per-bacterium levels of DNA and A(T) varied six- and threefold, respectively, during a 6-h period of decreasing growth rate for an unidentified pseudomonad isolated from contaminated groundwater and grown in batch culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesion and growth rate of Clostridium cellulolyticum ATCC 35319 on crystalline cellulose

The rate of tritiated-thymidine incorporation into DNA was used to estimate Clostridium cellulolyticum H10 growth rates on Avicel cellulose, taking into consideration both the unattached cells and the cells adhered to the substrate. The generation time on cellobiose calculated from the data on cell density (4.5 h) agreed well with the generation time calculated by tritiated-thymidine incorporation (3.8 h). Growth on Avicel cellulose occurred when bacteria were adhered to their substrate; 80% of the biomass was detected on the cellulose. Taking into consideration attached and free bacteria, the generation time as determined by thymidine incorporation was about 8 h, whereas by bacterial-protein estimation it was about 13 h. In addition to the growth rate of the bacteria on the cellulose, the release of adhered cells constituted an important factor in the efficiency of the cellulolysis. The stage of growth influenced adhesion of C. cellulolyticum; maximum adhesion was found during the exponential phase. Under the conditions used, the end of growth was characterized by an acute release of biomass and cellulase activity from the cellulose. An exhaustion of the accessible cellulose could be responsible for this release.

Correlation of nonspecific macromolecular labeling with environmental parameters during [(3)H]Thymidine incorporation in the waters of southwest florida

During routine [(3)H]thymidine incorporation measurements of environmental samples, significant amounts of radioactivity are often incorporated into macromolecules other than DNA. Although the percentage of nonspecific labeling varies both temporally and spatially, the cause(s) of these variations remain unknown. Correlations between the percent incorporated radioactivity in DNA and a variety of experimental and environmental parameters measured in the Alfia River, Crystal River, Medard Reservoir, and Bayboro Harbor were examined. The amount of radioactivity incorporated into DNA ranged from 6 to 95% ([Formula: see text]; n=121). Nonspecific labeling began immediately upon the addition of [(3)H]thymidine and was linear over time. Labeling patterns were independent of both the amount of thymidine added and cell-size fraction. A two year study of Bayboro Harbor indicated no conclusive relationship between nonspecific labeling and seasonality. The amount of radioactivity incorporated into DNA was inversely correlated with total rates of thymidine incorporation and a strong diurnal pattern was observed in the Crystal River. No consistent relationship was observed between labeling patterns and primary productivity, chlorophylla, particulate DNA, dissolved DNA, bacterial cell numbers, temperature, salinity, and dissolved organic carbon. The only relationship with dissolved inorganic nutrients (N and P) occurred in the Crystal River. In this phosphate limited river, the percent of radioactivity incorporated into DNA was positively correlated with phosphate concentrations. These results indicate that nonspecific labeling is not dependent on any one parameter but may be a function of many interacting environmental factors or a function of the specific ambient bacterial population.

Growth and metabolic flexibility in groundwater bacteria

Groundwater bacteria isolated from an oligotrophic-saturated soil showed a mixed strategy of economized metabolism and migration when grown in a continuous-flow column system simulating poor or nutrient-amended growth conditions. The cells were generally <0.5μm in diameter in pure groundwater, but doubled in size when the concentration of dissolved organic carbon and phosphate in groundwater was increased 10-fold. The biomass, estimated from analysis of muramic acid (MuAc) in cell wall peptidoglucans, increased at the same time by a factor of 5 when the solid support in the columns was gravel and by a factor of 10 when it was glass beads. Bacteria in pure groundwater stored 10 times more of the energy-rich polysaccharide, poly-β-hydroxybutyric acid (PHB), than bacteria in enriched groundwater, and those cells that were attached to the gravel stored 10 times as much as cells in the interstitial pore water. Once phosphate was added to groundwater, stored PHB was metabolized. The proportion of free-living to attached bacteria was 2 to 10 times higher in enriched compared with pure groundwater indicating a mass transport of cells as the carrying capacity of their habitat rose.

Survival and activity of Streptococcus faecalis and Escherichia coli in petroleum-contaminated tropical marine waters

The in situ survival and activity of Streptococcus faecalis and Escherichia coli were studied using membrane diffusion chambers in tropical marine waters receiving oil refinery effluents. Protein synthesis, DNA synthesis, respiration or fermentation, INT reduced per cell, and ATP per cell were used to measure physiological activity. Cell densities decreased significantly over time at both sites for both S. faecalis and E. coli; however, no significant differences in survival pattern were observed between S. faecalis and E. coli. Differences in protein synthesis between the two were only observed at a study site which was not heavily oiled. E. coli was more active in protein synthesis and respiration than S. faecalis at both oiled and unoiled sites, and the percentage of the E. coli population that was respiring was significantly higher than S. faecalis fermenting cells at both sites. However, S. faecalis cells were more active in DNA synthesis and higher in ATP content than E. coli cells at both sites. Although fecal streptococci have been suggested as a better indicator of fecal contamination than fecal coliforms in marine waters, in this study both E. coli and S. faecalis survived and remained physiologically active for extended periods of time. These results suggest that the fecal streptococci group is not a better indicator of fecal contamination in tropical marine waters than the fecal coliform group, especially when that environment is high in long-chained hydrocarbons.

Dual-Label Radioisotope Method for Simultaneously Measuring Bacterial Production and Metabolism in Natural Waters

Bacterial production and amino acid metabolism in aquatic systems can be estimated by simultaneous incubation of water samples with both tritiated methyl -thymidine and 14 C-labeled amino acids. This dual-label method not only saves time, labor, and materials, but also allows determination of these two parameters in the same microbial subcommunity. Both organic carbon incorporation and respiration can be estimated. The results obtained with the dual-label technique are not significantly different from single-radiolabel methods over a wide range of bacterial activity. The method is particularly suitable for large-scale field programs and has been used successfully with eutrophic estuarine samples as well as with oligotrophic oceanic water. In the mesohaline portion of Chesapeake Bay, thymidine incorporation ranged seasonally from 2 to 635 pmol liter −1 h −1 and amino acid turnover rates ranged from 0.01 to 28.4% h −1 . Comparison of thymidine incorporation with amino acid turnover measurements made at a deep, midbay station in 1985 suggested a close coupling between bacterial production and amino acid metabolism during most of the year. However, production-specific amino acid turnover rates increased dramatically in deep bay waters during the spring phytoplankton bloom, indicating transient decoupling of bacterial production from metabolism. Ecological features such as this are readily detectable with the dual-label method.

Growth and comparative physiology of Klebsiella oxytoca attached to granular activated carbon particles and in liquid media

Experiments were performed to evaluate the comparative growth and physiology of Klebsiella oxytoca grown attached to granular activated carbon particles (GAC) and in liquid medium. Laboratory studies showed that when this organism attached to GAC, the growth rate was enhanced more than 10 times in the presence of glutamate, a substrate that adsorbed to the surface. No differences were observed if the substrate was glucose, which did not adsorb to GAC. Cellular [3H]thymidine uptake was used to estimate DNA biosynthesis. Attached bacteria grown in a minimal nutrient medium containing 20.0 mg/liter glutamate took up 5 times more [3H]thymidine than cells grown in suspension. [3H]uridine was used as a measure of RNA turnover. Attached cells were shown to assimilate 11 times more [3H]uridine than cells in liquid media. Cell size measurements were performed by differential filtration. Cells grown in a minimal medium with 20.0 mg/liter glutamate decreased in size over time, with 62% of the total number passing through a 1.0 micron filter after 9 days incubation. In the same period, 39% of a cell population that was grown on GAC passed through a 1.0 micron filter. These studies indicate that GAC provides an interfacial environment for the enhanced growth of K. oxytoca when glutamate is the substrate.

Influence of Physical Disruption on Growth of Attached Bacteria

Attached bacterial populations cultured without an exogenous carbon source or grown in conjunction with attached diatoms incorporated [ 3 H]thymidine at a rate between four and five times lower than that of replicate bacterial populations which were dispersed before being assayed.

Preservation of ATP in Hypersaline Environments

High concentrations of particulate ATP were found in the anoxic brines of the Orca Basin and East Flower Garden, Gulf of Mexico. Other measurements indicative of growth and respiration suggested that the microbial community in the brines was inactive, but somehow the ATP associated with the cells persisted. Conceivably, when cells growing just above the interface sank into the brine, the increased osmotic stress could elicit an osmoregulatory response resulting in increased ATP. It was also possible that hydrolytic enzymes were inactivated, resulting in the preservation of ATP. Experiments in which a culture of marine bacteria was suspended in menstrua of different salinities comparable to those found across the Orca Basin interface revealed that as salinity increased, ATP increased three- to sixfold. Within 24 h the ATP fell to its initial level and remained at that concentration for 3 days, at which time the experiment was terminated. In contrast, the control suspensions, at a salinity of 28% (grams per liter) had 1/10th of the initial ATP concentration when the experiment was ended. Cells were also exposed to killing UV irradiation, enabling us to demonstrate with absolute certainty that cellular ATP could be preserved. At the end of the experiment, the viable component of the population was reduced by orders of magnitude by UV irradiation, but the ATP levels of the cells suspended in brine did not decrease. In certain environments it appears that the conventional analytical tools of the microbial ecologist must be interpreted with caution.