Specific Growth Rate Of Bacteria Research Articles

Role of nutrient limitation and stationary-phase existence in Klebsiella pneumoniae biofilm resistance to ampicillin and ciprofloxacin.

Biofilms formed by Klebsiella pneumoniae resisted killing during prolonged exposure to ampicillin or ciprofloxacin even though these agents have been shown to penetrate bacterial aggregates. Bacteria dispersed from biofilms into medium quickly regained most of their susceptibility. Experiments with free-floating bacteria showed that stationary-phase bacteria were protected from killing by either antibiotic, especially when the test was performed in medium lacking carbon and nitrogen sources. These results suggested that the antibiotic tolerance of biofilm bacteria could be explained by nutrient limitation in the biofilm leading to stationary-phase existence of at least some of the cells in the biofilm. This mechanism was supported by experimental characterization of nutrient availability and growth status in biofilms. The average specific growth rate of bacteria in biofilms was only 0.032 h(-1) compared to the specific growth rate of planktonic bacteria of 0.59 h(-1) measured in the same medium. Glucose did not penetrate all the way through the biofilm, and oxygen was shown to penetrate only into the upper 100 micro m. The specific catalase activity was elevated in biofilm bacteria to a level similar to that of stationary-phase planktonic cells. Transmission electron microscopy revealed that bacteria were affected by ampicillin near the periphery of the biofilm but were not affected in the interior. Taken together, these results indicate that K. pneumoniae in this system experience nutrient limitation locally within the biofilm, leading to zones in which the bacteria enter stationary phase and are growing slowly or not at all. In these inactive regions, bacteria are less susceptible to killing by antibiotics.

Specific growth rate of bacterioplankton, determined at constant temperature, as an indicator of deterioration in water quality

The specific growth rate (SGR) of natural populations of bacterioplankton, from three lowland watercourses in the northeastern part of England, was measured at intervals over 15 months using a batch-culture method. SGR of the bacteria from one watercourse showed seasonal periodicity with notably low values (<0.01 h -1 ) in winter which coincided with acid conditions. SGR of bacteria from the other two watercourses, which were permanently circumneutral, showed irregular periodicity and notably low values were never recorded. Thus, SGR is an easily determined indicator which may be used to recognize the inhibition of bacterioplankton, which is brought about by adverse water quality, and which potentially leads to reduction in biopurification capacity.

Bacterial growth dynamics in activated sludge batch assays

Aerobic batch reactors are often used to estimate the maximum specific growth rates of bacteria in wastewater treatment environments. Results from these reactors vary, and they are sometimes confusing because they do not represent the bacterial populations in the original wastewater environment, i.e. in situ. For the first time in batch reactors, we present the in situ growth dynamics of these bacterial populations. We simultaneously measured bacterial numbers and growth rate, oxygen uptake rates (OUR), soluble COD and biomass COD (mg.l −1). With a substrate to biomass (S o/X o) ratio of 1.2, bacterial specific growth rates, measured using the thymidine growth assay, increased from 1 to 4.5 d −1. During the same period, the initial OUR remained relatively constant, with an OUR-based estimate of the maximum specific growth rate of 3.6 d −1. These observations challenge the fundamental theory of the batch assay that bacteria are growing at their maximum rate under substrate saturating conditions while the yield coefficient remains constant. Our results confirm that the batch reactor environment induces changes in the bacterial physiology and/or community structure compared to the original treatment environment, even at low S o/X o ratios. We discuss how, simultaneously using both OUR and thymidine assays, gives more information about how the cell allocates its energy resources between new cell synthesis and cell maintenance.

Uncoupled Responses of Bacterial and Algal Production to Storm-induced Mixing in Lake Biwa

Production of bacteria and phytoplankton was examined over a three week period during the storm season (August-September) in the South Basin (water depth, 4 m) of Lake Biwa, Japan. Passage of two typhoons caused drastic changes in physical and nutrient conditions, including pulsed increases in the concentration of soluble reactive phosphorus (SRP) associated with sediment resuspension. In response to these meteorological events, phytoplankton increased substantially; up to 6-fold and 3-fold higher values of chlorophyll a and primary production relative to average prestorm levels were observed during the storm period. In contrast, bacterial abundance and production increased little after the storm events. The abundance, production rate, and specific growth rate of bacteria were not significantly correlated with primary production (p>0.4). Furthermore, the ratios of bacterial : primary production were high (maximum, 1.3), suggesting that bacterial carbon demand occasionally exceeded primary production. These results are consistent with the hypothesis that organic carbon from non-phytoplanktonic origins (i.e. allochthonous and littoral organic carbon) are important for bacteria in freshwater lakes. Notably, there was a highly significant correlation (p=0.003; r=0.627; n=20) between specific growth rates of bacteria and SRP concentrations, suggesting that bacterial growth was limited by P. We conclude that the coupling of bacterial and algal responses to the typhoon disturbance was weak in Lake Biwa. The results support a recent model of the lacustrine microbial loop, which suggests that bacteria are largely driven by external carbon supplies and that bacteria may compete with phytoplankton for P.

Microbial processes in cold oceans. I. Relationship between temperature and bacterial growth rate

Despite the obvious relevance of the high latitude oceans to models and budgets of biogenic carbon, the seasonal patterns of energy flow through the lower food web in this region are poorly understood. It has been suggested that, in high latitude and cold oceans, the rates of bacterial metabolism and growth are low and are depressed to a much greater degree than those of co-occurring phytoplankton and metazoan heterotrophs. The low-temperature suppression of bacterial growth would reduce microbial food web activity, bacteria would consume and recycle less primary production and more phytoplankton carbon would be available to metazoan grazers. The implications of this scenario for models of oceanic carbon flow are profound. In this paper, we present an analysis of 66 published studies on temperature and growth rate for bacteria from the World Ocean, including polar regions, and examine the results of a field investigation of bacterioplankton growth in seasonally cold Newfoundland (eastern Canada) coastal waters. Based upon the analysis of published data, where approximately 50 % of the observations were from environments less than or equal to 4 degrees C, we report a weak (r(2) - 0.058, n = 231) relationship between specific growth rate (SGR) and temperature with a Q(10) = 1.5. The mean (0.39 to 0.41 d(-1)) and median (0.25 to 0.29 d(-1)) SGR of bacteria from cold (less than or equal to 4 degrees C) and warm (>4 degrees C) waters were not significantly different. For both the published data as well as for the field study in Conception Bay, Newfoundland, the SGR was significantly greater (p < 0.01) when computed from empirical thymidine conversion factors than from theoretical or literature derived thymidine conversion factors. Our analysis suggests that the growth rates of bacterioplankton from cold and temperate oceans are similar at their respective ambient temperatures, when the appropriate conversion factors are used to compute growth. We propose that bacteria-based food webs and microbial trophic pathways are as important in overall energy and material cycling in high latitude oceans as they are at lower latitudes.

Biomass, production, and specific growth rate of bacterioplankton and coupling to phytoplankton in an oligotrophic lake

Production of bacterioplankton and phytoplankton was analyzed in oligotrophic Lawrence Lake, Michigan, over a 2‐yr period. Variables examined were temperature, bacterial numbers and biovolumes, bacterial production and specific growth rates (µ), phytoplanktonic biomass and production, and alkaline phosphatase activity. Algal and bacterial production varied similarly on temporal and spatial scales; some differences in vertical patterns were evident during summer stratification. Values for µ ranged from 0.2 d‒1 during winter to 2.6 d‒1 in midsummer. Decreases in specific growth rates of bacteria coincided with the onset of heavy CaCO3 precipitation and with increased alkaline phosphatase activities. µ was close to predicted maximal values during periods of mixing but was depressed in upper layers during summer. Temperature showed significant bivariate rank correlations with all variables. With temperature controlled, µ did not show significant partial correlations with algal chlorophyll or production, consistent with a minor role of dissolved organic carbon from phytoplankton for bacterial growth. Low and high estimates of bacterioplanktonic production over 2 yr exceeded that of phytoplankton by factors of 1.33 and 3.35. Net metabolism in the pelagic zone was heterotrophic, a state likely maintained by littoral macrophytic and periphytic production. Apparent coupling between phyto‐ and bacterioplankton stemmed mainly from similar responses of each component to common regulating factors rather than from direct metabolic links.

Microbial activity and phosphorus dynamics in eutrophic lake sediments enriched with Microcystis colonies

SUMMARY1. Sediments from hypereutrophic Lake Vallentunasjön were enriched with Microcystis colonies from the lake water, thereby simulating the conditions after the autumn sedimentation. Release of phosphorus to the overlying lake water was followed during 2–3 weeks in the laboratory. X‐ray microanalysis of individual Microcystis and bacterial cells, and chemical phosphorus fractionation, were used to assess the phosphorus pool size in different fractions of the sediment.2. Benthic Microcystis colonies, most of these having survived within the sediment for 1 year or more, were less susceptible to decomposition, and the specific growth rate of bacteria in their mucilage was lower than for other sediment bacteria.3. Pelagic Microcystis colonies from late August were resistant to decomposition, when placed on the sediments. When Microcystis colonies from a declining pelagic population in October were added to the sediments, however, a substantial fraction of these colonies was decomposed. The specific growth rate of mucilage bacteria was five times higher than for other sediment bacteria.4. Release of molybdate‐reactive phosphorus to the overlying lake water was larger from sediment cores enriched with Microcystis colonies than from control cores. Chemical phosphorus fractionation showed a decrease in organic‐bound phosphorus (residual P).5. X‐ray microanalysis showed that the phosphorus bound in Microcystis cells decreased by ‐0.300 mg g−1 DW in the October experiment, due both to a decrease in biomass (i.e. mineralization) and to a decrease in phosphorus content in the remaining cells. Heterotrophic bacteria increased their cellular concentration of phosphorus. The net release of phosphorus from the Microcystis and bacterial pools corresponded to 74% of the decrease of organic‐bound phosphorus in the chemical phosphorus fractionation, and to 65% of the decrease of total phosphorus in the upper 0–1 cm of the sediment.6. Benthic bacteria and cyanobacteria may thus contribute significantly to changes in phosphorus content and turnover of the sediment by changes in their biomass, turnover rate and cellular phosphorus content.

Biomass and production of bacteria and phytoplankton during the spring bloom in the western North Atlantic Ocean

During the 1989 spring bloom in the western North Atlantic, we estimated the biomass and productivity of bacteria and phytoplankton at two sites (40 and 45°N) representing different water masses. At 40°N, almost all of the phytoplankton carbon could be accounted for by photosynthetic nanoplankton and picoplankton; in contrast, at 45°N, only about half was thus accounted, implying a substantial contribution by photosynthetic microplankton. At both sites, bacterial abundance was quite high (up to 2 × 109 cells l−1), and the rates of bacterial production assessed by incorporation of [3H]thymidine (up to 8 pmol l−1 h−1) and [3H]leucine (up to 240 pmol l−1h−1) were significant. Specific growth rates of bacteria based on [3H]thymidine incorporation were 0.08–0.25 day−1. Taken together, our measurements and assumptions implied a demand for primary production in the order of 16–36% over the euphotic zone or 24–78% over the upper 100 m in the water column. We conclude that ultraphytoplankton and bacteria played significant roles in the flux of carbon during the 1989 North Atlantic spring bloom.

Utility of phenomenological models for describing temperature dependence of bacterial growth

We compared three unstructured mathematical models, the master reaction, the square root, and the damage/repair models, for describing the relationship between temperature and the specific growth rates of bacteria. The models were evaluated on the basis of several criteria: applicability, ease of use, simple interpretation of model parameters, problem-free determination of model parameters, statistical evaluation of goodness of fit (chi 2 test), and biological relevance. Best-fit parameters for the master reaction model could be obtained by using two consecutive nonlinear least-square fits. The damage/repair model proved to be unsuited for the data sets considered and was judged markedly overparameterized. The square root model allowed nonproblematical parameter estimation by a nonlinear least-square procedure and, together with the master reaction model, was able to describe the temperature dependence of the specific growth rates of Klebsiella pneumoniae NCIB 418, Escherichia coli NC3, Bacillus sp. strain NCIB 12522, and the thermotolerant coccobacillus strain NA17. The square root and master reaction models were judged to be equally valid and superior to the damage/repair model, even though the square root model is devoid of a conceptual basis.

Inhibition of microbial growth and metabolism by excess turbulence

Excess turbulence caused by high-intensity stirring inhibited microbial growth and metabolism. In stirred tank bioreactors, the growth rate and lysine biosynthesis decreased in Brevibacterium flavum beyond 900 rpm, the growth rate of Trichoderma reesei on wheat straw beyond 150 rpm, and the growth rate of Saccharomyces cerevisae beyond 800 rpm. The term turbohypobiosis was introduced to describe this inhibition. Turbohypobiosis was characterized by a stress factor F(str) expressing the interaction of medium flow with microbial cells in local turbulent zones, dependent on the energy distribution of the stirring regime. Lysine synthesis was inhibited at significantly lower F(str) values than the growth of B. flavum. The main reason for the inhibition was shear effects causing decreased adenosine triphosphate (ATP) generation, lower O(2) uptake, and lower specific growth rate of bacteria.

Bacterial production, heat production and ATP-turnover in shallow marine sediments

Seasonal variation in bacterial numbers and biomass, ATP concentration, heat production, bacterial production and basic sediment chemistry was followed in shallow marine sediments off the Forsmark Nuclear Power Plant on the Swedish Baltic coast. Production and specific growth rate of bacteria were strongly temperature dependent although the sedimentation of diatoms in the spring caused a significant increase in microbial activity in spite of a low temperature. In situ bacterial doubling time and ATP-turnover values indicated that a large portion of the sediment bacteria was “dormant” or non-growing at all seasons, even in summer. Average growth yield of the bacterial community, calculated from the bacterial production and heat production measurements, varied between 17 and 40 % .

Growth of bacteria in seawater filtered through 0.2 µm Nuclepore membranes. Implications for dilution experiments

Dilution experlments were conducted in the Caribbean and Sargasso Seas in an attempt to measure bacterial growth under reduced grazing pressure. In this type of experiment, a small volume of the intact plankton sample is diluted into the same seawater from which all organisms have presumably been removed by filtration We noted that d ~ l u e n t prepared by vacuum filtration (< 100 mm Hg pressure) of natural seawater through 0.2 pm Nuclepore membranes contained bacterla which could be retained by the same membranes upon refiltration Upon ~ncubat ion, these bacteria rapidly accumulated 3H-amino acids and grew at high rates (0.18 h') The literature supports the evidence of ultramicrobacteria (those which might be expected to pass through 0.2 pm membranes): these may have passed into the diluent but were subsequently retained on 0 2 pm membranes poss~bly because they increased in cell size, formed ultramicrocolonies, or were aspherical In shape so that the orientation in relation to the membrane pore determined whether the cell was filtered or retained. Although the apparent specific growth rate of bacteria was in inverse relation to the degree of sample dilution, interpretable as a consequence of grazing on bacteria, the growth of bacteria in the diluent made it problematic to consider the dilution experlments in the conventional manner. It IS likely that the 0.22 pm cellulose ester membranes used by many others who have performed such experiments would be much more effective in retaining ultramicrobacteria.

Multistep kinetics: Choice of models for the growth of bacteria

Since the work of Monod, it has generally been taken for granted that the specific growth rate of bacteria is a hyperbolic function of the limiting nutrilite. However, there have been reports where the deviation from a hyperbola was found such that the specific growth rate rises proportionally to substrate concentration but then increases very little more after a critical concentration is reached. Also, cases have been found where there are several independent mechanisms of substrate uptake and the dependency of growth rate on substrate concentration is the sum of the processes. In this paper I discuss the available data and the previous theoretical considerations and present computer programs to fit the several statistical and metabolic models. Also presented are the fits to an actual sample of high precision growth data recently obtained in our laboratory using a computer-linked, double-beam spectrophotometer.

Derivation of a generalised monod equation and its application

AbstractA generalised growth rate equation is derived which relates the specific growth rate of bacteria to the concentration of a limiting nutrient in a bacterial culture. Monod's simple hyperbolic and Teissier's exponential equations are shown to be two special cases of this general equation. It is also revealed that the so‐called Michaelis‐Menten constant in Monod's simple equation is inversely proportional to the maximum specific growth rate.

Kinetics of the liquid‐phase oxidation of acid ferrous sulfate by the bacterium Thiobacillus ferrooxidens

AbstractThe kinetics of the batch‐wise liquid‐phase oxidation of ferrous sulfate by the organism Thiobacillus ferrooxidans has been studied over a range of temperatures from 20°C to 31°C and in the presence of an abundant supply of oxygen, carbon dioxide, and other nutrients.The rate of oxidation was found to be accurately described by the equation where t = time hr, S = concentration of ferrous ions g Fe++/1., μm = maximum specific growth rate of bacteria, hr−1. Y = mass of bacteria produced per gram of iron oxidized g/g, K = saturation constant, g Fe++/l., and X = concentration of bacteria g/1.The value for the maximum specific growth rate, μm, was found to vary from 0.12 hr−1 at 20°C to 0.20 hr−1 at 31°C, while the value for the saturation constant K varied randomly between 1 and 2 g/1.A method has also been described which permitted evaluation of the relevant rate constants μm and K without direct knowledge of the bacterial population. This method was found to yield values of μm and K which agreed with values determined accurately by a statistical regression analysis of the experimental data.

Periodic changes of beta-galactosidase in Escherichia coli B in the chemostat.

In the course of long-term cultivation of Escherichia coli in a chemostat under conditions of specific growth rate limitation by lactose, selection takes place of strains which produce ~-galactosidase constitutively at a rate 4--5 times higher than the original strain (Novick & Horiuchi, 1961; Horiuchi, Tomizawa & Norick, 1962). These, so called hyper strains are in many ways different from the normal consti tutive strains. Materials and methods are described in the previous paper (Vojtiw Sikyta & Slez~k, 1968). Enzyme synthesis was followed in a chemostar using different C-sources in concentrations limiting the specific growth rate of bacteria. The experiments were run in such a way tha t after selection of the hyper strain had occurred in a lactose containing medium, the lactose containing stock medium was replaced by stock medium containing the particular C-source. In all experiments the dilution rate of 0.2 hour -1 was used and the substrates concentration in the inflowing medium was adjusted to such values tha t the cell concentration in the steady state was the same (0.32 mg dry weight/ /ml). In the course of the cultivation of the hyper strain in a chemostat when the specific growth rate is limited by glucose, the specific activity of ~-galactosidase is under these conditions after a t ta ining the steady state 30% higher t han during cultivations in a lactose-containing medium (Fig. 1). This increase m a y be explained by the absence of repression of endogenous intermediates of galactose metabolism, c.f. UDP galactoside which are formed during growth on lactose (Vojtitek, Sikyta & Slez~k, 1968). During the cultivation of hyper strain in a ehemostat when the specific growth rate is limited by galaetose (Fig. 1) the specific activi ty of the enzyme sharply dropped to the value corresponding approximately to the constitutive strain. The reason for this decrease could be the repression of enzyme synthesis by U D P galactoside. I t is evident from l~ig. 1 tha t the values of specific activi ty during cultivation in media with glucose change in a sense which is quite contrary to changes in media with galactose. Since these two compounds together form the molecule of lactose we wished to find out what would be the course of specific activities in a medium with equivalent amounts of glucose and galactose (both in concentrations of 1 .4 .10 -a ~). I t may be seen from Fig. 2 tha t when a lactose-containing medium is replaced by a glucose -k galactose medium, values