Comparison of temperature effects on soil respiration and bacterial and fungal growth rates

Temperature is an important factor regulating microbial activity and shaping the soil microbial community. Little is known, however, on how temperature affects the most important groups of the soil microorganisms, the bacteria and the fungi, in situ. We have therefore measured the instantaneous total activity (respiration rate), bacterial activity (growth rate as thymidine incorporation rate) and fungal activity (growth rate as acetate-in-ergosterol incorporation rate) in soil at different temperatures (0-45 degrees C). Two soils were compared: one was an agricultural soil low in organic matter and with high pH, and the other was a forest humus soil with high organic matter content and low pH. Fungal and bacterial growth rates had optimum temperatures around 25-30 degrees C, while at higher temperatures lower values were found. This decrease was more drastic for fungi than for bacteria, resulting in an increase in the ratio of bacterial to fungal growth rate at higher temperatures. A tendency towards the opposite effect was observed at low temperatures, indicating that fungi were more adapted to low-temperature conditions than bacteria. The temperature dependence of all three activities was well modelled by the square root (Ratkowsky) model below the optimum temperature for fungal and bacterial growth. The respiration rate increased over almost the whole temperature range, showing the highest value at around 45 degrees C. Thus, at temperatures above 30 degrees C there was an uncoupling between the instantaneous respiration rate and bacterial and fungal activity. At these high temperatures, the respiration rate closely followed the Arrhenius temperature relationship.     

The influence of daylength,light intensity and temperature on the growth rates of planktonic blue-green algae

The in vitro growth rates under continuous light of the four dominant blue-green algae in Lough Neagh, Anabaena flos-aquae Bréb., Aphanizomenon flos-aquae Ralfs fa. gracile Lemm., Oscillatoria agardhii Gom. and Oscillatoria redekei van Goor were slower than in situ rates from Lough Neagh that had been corrected for hours of light received by the algae. However, by culturing on a 6: 18 light-dark cycle in vitro growth rates were obtained that were similar to the in situ rates. Under continuous light small species showed the fastest growth with Oscillatoria redekei the dominant species. However, this pattern was almost completely reversed under the light-dark cycle with Oscillatoria redekei only exhibiting the fastest growth rate under low light conditions. This observation showed agreement with Lough Neagh field data which showed that Oscillatoria redekei reached its maximum crop in April while the other three species were dominant during the summer months. Compared to the generally assumed high thermal tendency of blue-green algae the temperature maxima of the four species were low. No growth was observed at 35°C for any species while Anabaena flos-aquae was severely inhibited at 25°C.     

Chelators enhanced biocide inhibition of planktonic sulfate-reducing bacterial growth

Biocides are currently the primary mitigation method to control sulfate-reducing bacteria (SRB) in biofouling, reservoir souring and microbiologically influenced corrosion. Increasingly restrictive environmental regulations and safety concerns on biocide uses demand more efficient dosing of biocides. Chelators have been known to enhance antibiotics because of their properties such as increasing the permeability of the outer cell membrane of Gram-negative bacteria. Two readily biodegradable chelators, ethylenediaminedisuccinate (EDDS) and N-(2-hydroxyethyl)iminodiacetic acid (HEIDA) disodium salts that are touted as potential replacements of ethylenediaminetetraacetic acid (EDTA), were evaluated as potential biocide enhancers for glutaraldehyde and tetrakis hydroxymethyl phosphonium sulfate (THPS) in their inhibition of planktonic SRB growth. Desulfovibrio vulgaris ATCC 7757 and Desulfovibrio desulfuricans ATCC 14563 were grown in modified ATCC 1249 medium and in enriched artificial seawater, respectively. Laboratory tests in 100 ml anaerobic vials showed that EDDS or HEIDA alone did not inhibit SRB growth. However, when EDDS or HEIDA was combined with glutaraldehyde or THPS, each of them enhanced the biocide inhibition of planktonic SRB growth.     

The planktonic and benthic bacterial populations of Lough Neagh

The planktonic and benthic bacterial populations of Lough Neagh, Northern Ireland, were studied over a one-year period. Direct counts of bacteria in the water column averaged 6 times 10⁷/ml with limited spatial or temporal variation; viable counts, however, showed a pronounced late spring maximum of 1.7 times 10⁶/ml and were consistently higher at a littoral sampling station. Direct counts of bacteria in the profundal sediments averaged 8 times 10⁹/ml whilst viable benthic counts rose steeply during spring to reach a June maximum of 1 times 10⁸/ml. Direct: viable count ratios were much greater in the more sandy littoral zone. The predominant benthic isolate was an Aeromonas sp. which was also common in samples from the water column. These results confirm the eutrophic status of Lough Neagh indicated by other biological and chemical surveys.     

Loss processes influencing growth of planktonic bacterial populations in Lake Constance

The fate of bacterial production in a deep mesotrophic lakehas been investigated on the basis of a multiple approach combiningfield and experimental studies. Bacterial production gains asestimated by measurements of methyl-[³H]thymidine incorporationinto macromolecules appeared to be more or less balanced bycorresponding grazing losses. This was suggested by consideringabundance and grazing potential of presumed grazers as wellas by following in time the binding of labelled bacteria bylarger sized organisms. Moreover, strong increases in bacterialnet growth were always observed after removal of grazers fromthe water samples. As was indicated by independent approaches,phagotrophic microflagellates were mainly responsible for theobserved grazing losses. Support for the importance of alternativeloss processes such as sinking or autolysis was given neitherby field observations nor by long-term expenments with exclusionof grazers. It is concluded that phagotrophic microflagellatesmay be regarded as important functional components of planktoniccommunities in freshwater lakes.     

The effects of temperature and growth rate on the proportion of unsaturated fatty acids in bacterial lipids

The effects of temperature and growth rate on the fatty acid composition of the extractable lipids of four mesophilic and three psychotrophic bacteria were examined. Two of the mesophiles (Escherichia coli and Pseudomonas aeruginosa) increased the proportion of unsaturated fatty acids in their lipids with decreasing temperature over their whole growth temperature range. The other mesophiles (Enterobacter aerogenes and Lactobacillus casei) increased the proportion of unsaturated fatty acids with decreasing temperature only over the lower half of their growth temperature ranges. The psychrotrophs Pseudomonas fluorescens and Enterobacter sp. had a constant proportion of unsaturated acids over the lower half of their growth temperature range, while the psychotrophic Lactobacillus sp. showed no consistent change in its unsaturated fatty acid composition with temperature. All species showed some variation of unsaturated fatty acid composition with growth rate at the highest and lowest growth temperatures, although such variations were small in some species (Ent. aerogenes and Lactobacillus sp.).     

The effects of temperature and prey density on the development rates and growth of damselfly larvae (Odonata: Zygoptera)

Abstract. 1. The effects of prey density and temperature on the feeding and development rates of several late instars of the larvae of three common European damselflies ( Lestes sponsa (Hansemann), Coenagrion puella (L.) and Ischnura elegans van der Linden) were investigated in a laboratory experiment.
2. Functional responses were used to estimate maximum feeding rates. Maximum feeding rates were compared between species, instars and temperatures by expressing prey consumption in terms of prey biomass consumed per unit predator biomass. Lestes was capable of feeding at almost twice the rate of either Coenagrion or Ischnura.
3. Higher feeding rates led to faster development rates and there was an interaction between species and temperature. With the exception of those with very low feeding rates, larvae maintained at higher temperatures, but similar feeding rates, developed faster. Under similar conditions of temperature and feeding rate, Lestes larvae developed faster than larvae of either Coenagrion or Ischnura.
4. Faster development rates at similar rates of food intake were achieved at the cost of reduced size-increases between instars.
5. The differences in the responses of the three species are discussed in the light of their respective life histories, and with reference to a recent model of population regulation in damselflies.     

The influence of irradiance,photoperiod and temperature on the growth kinetics of three planktonic diatoms

The influence of irradiance, photoperiod and temperature was determined for the growth kinetics of the diatoms Aulacoseira subarctica, Stephanodiscus astraea and Stephanodiscus hantzschii and the results compared with those of cyanobacteria. Irradiance and photoperiod relationships were qualitatively similar to those for cyanobacteria in that: (1) growth rate (K) was proportionally greater under short photoperiods, with ratios of K under continuous light to K under 3:21 light:dark (LD) cycles of 1·50, 1·80 and 2·96 for A. subarctica, S. astraea and S. hantzschii respectively; (2) at subsaturating irradiances, K was proportional to irradiance and independent of temperature with a negligible predicted maintenance growth rate requirement. Apparent growth efficiencies (GE) at subsaturating irradiances were 0·26±0·03, 0·42±0·03 and 0·50±0·03 divisions mol^-1m² for A. subarctica, S. astraea and S. hantzschii with the values for Stephanodiscus species comparable to values for Oscillatoria species. Under a 3:21 LD cycle at 4 °C, light-saturated growth rates were 0·066±0·004, 0·197±0·033 and 0·285±0·018 divisions day^-1 for A. subarctica, S. astraea and S. hantzschii. S. hantzschii growth rate at 4 °C exceeded maximum Oscillatoria growth rates at 23 °C and the S. astraea growth rate at 4 °C was equivalent to O. agardhii growth rate at 20 °C. Temperature increases above 4 °C gave Q₁₀ values between 4 °C and 12 °C of 3·68, 2·39 and 1·92 for A. subarctica, S. astraea and S. hantzschii, but higher temperatures resulted in minor increases in K. S. astraea growth rate peaked at 16 °C, declining sharply at higher temperatures. February to March in situ growth rates in Lough Neagh, mean temperature 4·3 °C, showed that the A. subarctica in situ K of 0·058 divisions day^-1 was close to the laboratory K at 4 °C, but that S. astraea in situ K of 0·101 divisions day^-1 was lower than the laboratory K at 4 °C.     

Ultraviolet and temperature effects on planktonic rotifers and crustaceans in northern temperate lakes

1. Anthropogenic stressors such as climate change, ozone depletion and acidification may act in concert to alter ultraviolet (UV) light and temperature regimes in freshwater ecosystems. These physical and chemical changes will inevitably affect zooplankton community dynamics, but little is known about their relative effects on different species in natural communities. During spring, species that migrate to surface waters to take advantage of warmer temperatures may be especially vulnerable as UV levels can be high. 2. The objective of this study was to investigate the in situ effects of UV and temperature on a natural assemblage of planktonic rotifers and crustaceans during the spring. We performed in situ exposure experiments in two lakes with different surface temperatures. 3. Exposure to UV had a significant effect on the abundance and/or reproduction of four rotifers: Gastropus spp., Kellicottia bostonensis, Kellicottia longispina, Keratella spp.; two cladocerans: Holopedium gibberum, Daphnia catawba, and one copepod: Leptodiaptomus minutus. Incubation under cooler temperatures had a negative effect on K. longispina and H. gibberum. Temperature and UV had a significant interactive effect on abundance and/or reproduction of L. minutus and Ploesoma truncatum. Our results indicate that changes in underwater UV and temperature can significantly influence the composition of the zooplankton community and ultimately food web dynamics.     

Cybernetic modeling of bacterial cultures at low growth rates: Mixed-substrate systems

A cybernetic model to predict the low-growth-rate behavior of bacteria in mixed-substrate environment is presented. Using only growth and maintenance parameters from single-substrate experiments, the model accurately predicts the simultaneous substrate utilization and maintenance energy effects in constant fed-batch cultures of Klebsiella oxytoca. The robustness of the model was examined more rigorously by perturbing glucose-limited fed-batch cultures with additions of arabinose, xylose, and fructose. In all cases, reasonable agreement of the model prediction with the experimental data was observed.     

In situ clearance rates of planktonic rotifers

The in situ clearance rates of several rotifer species from a small, temperate eutrophic lake were measured using three radioactive tracer cell-types, a bacterium (Aerobacter), a yeast (Rhodoto-rula), and alga (Chlamydomonas). Rates were below 10 µl/anim/h but varied significantly among species. Keratella cochlearis, Kellicottia bostoniensis, and Conochilus dossuarius ingested all three tracer cells but rates varied substantially with tracer cell-type. Polyarthra dolichoptera and P. euryptera ingested only the algal cells. Co-occurring forms of K. cochlearis and species of Polyarthra differed markedly in size and in tracer cell utilization, indicating niche diversification in food resources.     

Effects of temperature and food level on growth and development of a planktonic water mite

We analysed the relative effects of food availability and temperature on rates of growth and development of a predatory planktonic water mite, Piona exigua. Growth in length of mites fed Daphnia, Ceriodaphnia and Chydorus was analysed by Gompertz or von Bertalanffy curves; these curves were compared by parallel curve analysis. Growth rates of nymphs and adult female mites increased with temperature; the duration of the imagochrysalis stage decreased. Females grown at 10 °C were smaller at final size than females grown at 15 °C, 18 °C or 22 °C. Females reared at food levels of 15 or 30 prey l⁻¹ grew more slowly and were smaller than those provided with 60 or 120 prey l⁻¹. Nymphs grew more slowly when Daphnia were the only prey, than when smaller prey were available. Food level did not affect nymph growth at 10 °C or 15 °C, but growth at 18 °C or 22 °C may have been slowed at the lowest food levels. Synergistic effects of temperature and food level on nymph growth were apparent only from analysis of growth curves and not from stage duration data.     

Effect of drying and rewetting on bacterial growth rates in soil

The effect of soil moisture on bacterial growth was investigated, and the effects of rewetting were compared with glucose addition because both treatments increase substrate availability. Bacterial growth was estimated as thymidine and leucine incorporation, and was compared with respiration. Low growth rates were found in air-dried soil, increasing rapidly to high stable values in moist soils. Respiration and bacterial growth at different soil moisture contents were correlated. Rewetting air-dried soil resulted in a linear increase in bacterial growth with time, reaching the levels in moist soil (10 times higher) after about 7 h. Respiration rates increased within 1 h to a level >10 times higher than that in moist soil. After the initial flush, there was a gradual decrease in respiration rate, while bacterial growth increased to levels twice that of moist soil 24 h after rewetting, and decreased to levels similar to those in moist soil after 2 days. Adding glucose resulted in no positive effect on bacterial growth during the first 9 h, despite resulting in more than five times higher respiration. This indicated that the initial increase in bacterial growth after rewetting was not due to increased substrate availability.     

Resting metabolic rates in boid snakes: allometric relationships and temperature effects

Summary Resting metabolic rates (RMR) of 34 species from 18 genera of boas and pythons (Serpentes: Boidae), with body masses ranging from 2 to 67,800 g, were determined as oxygen consumption ( ) and carbon dioxide production ( ) at three ambient temperatures (T _a).The temperature coefficient of metabolism (Q₁₀) averaged 2.61 betweenT _a of 20–30°C and 2.65 between 30 and 34°C. The respiratory exchange ratio RE (= / ) increased slightly with increasingT _a (0.795 at 20°C, 0.819 at 30°C, and 0.834 at 34°C). Interspecific differences in Q₁₀ and RE were slight or insignificant.A multiple regression relating metabolism ( ) to mass andT _a explained 97% of the variance in the pooled interspecific data. The mass exponent was 0.806, which is approximately the same as reported for squamates and for all reptilian taxa combined. The mean within-species slope (0.732) was significantly less than the slope for pooled data, but did not differ significantly from 0.75. In 40 of 42 cases (14 species at 3T _a), within-species slopes did not differ from each other. Values of the adjusted mean Y, from covariance analysis, were significantly and positively correlated with mass, indicating that the mass coefficient increases with increasing mass.Considerable variation in metabolic rate is apparent both within and between ecological and taxonomic categories.Original metabolic data are available from the National Auxiliary Publications Services, c/o Microfiche Publication, P.O. Box 3153 Grand Central Station, New York, New York 10017, USA     

The effects of fungicides on the growth rates of thermophilous fungi

The effects of the fungicides Captan, Dicloran, Thiram, Verdasan and mercuric chloride (HgCl₂) on the radial and mycelial growth rates of thermophilous fungi isolated from living green leaves were studied. On controlplates Thermoascus aurantiacus andTorula thermophila had the highest radial growth rates whileMalbranchea pulchella var.sulfurea andTalaromyces duponti had the lowest growth rates. Good sporulation was seen on all control plates.With increasing concentrations of fungicides the growth rates were correspondingly retarded and sporulation was reduced. At het higher fungicide concentrations the hyphal tips and young hyphae were thicker and warty or granulated.Of the fungi studies,Aspergillus andMucor pusillus were the most tolerant species; they were capable of growth in more concentrations of fungicides compared with the other species.Talaromyces duponti andThermomyces lanuginosus emerged as the most sensitive species.Most marked reductions in the growth rates were produced by Thiram and Verdasan than by the other fungicides. All the ten thermophilous species studied were capable of growth with more concentrations of HgCl₂ than with the organo mercurial Verdasan.Six of the ten thermophilous species studied showed higher radial growth rates compared with the two fastest growing mesophilic species studied;Trlchoderma viride andZygorhynchus moelleri. While M. pusillus was capable of growth in dry weight at 0.05 ppm of all fine fungicides,Sporotrichum thermophile did not show mycelial growth with Verdasan at 0.05 ppm.Thermomyces lanuginosus showed reduced growth rates with Thiram and no mycelial growth with both HgCl₂ and Verdasan.     

The effects of major environmental factors and nutrient limitation on growth and encystment of planktonic dinoflagellate Akashiwo sanguinea

The bloom-forming dinoflagellate Akashiwo sanguinea is commonly observed in estuarine and coastal waters around the world. Annually recurrent blooms of this species have been observed in the coastal waters of China, particularly in the Sishili Bay, Yantai since 2004. However, limited studies have been conducted on the recurrence mechanism of A. sanguinea other than periodical monitoring of its population dynamics and associated environmental variables. Thus, to further explore the bloom and succession mechanisms of A. sanguinea in the field, we studied the effects of major nutritional components on the growth and encystment of A. sanguinea, as well as the effects of key environmental factors on the growth of A. sanguinea through a series of laboratory trials. Our results indicated that A. sanguinea was able to grow well within the temperature range of 20–25 °C, salinity range of 20 - 30, with the maximum laboratory irradiance of 78.14 μE m⁻² s⁻¹, and was able to survive and grow in low nutrient. However, lower concentrations of nutrients (e.g., nitrate, phosphate) and higher ammonium exerted different degrees of limiting effects on the growth of A. sanguinea, and induced 2.3–21.24% of vegetative cells to form resting cysts simultaneously in laboratory cultures. On the other hand, very limited or no cyst formation was observed in nutrient-replete or extremely low nutrient cultures, indicating the threshold effect of nutritional stress on the encystment of A. sanguinea. The physiological strategy of encystment of A. sanguinea in nutrient-limiting environment facilitates the survival and succession of A. sanguinea species in fluctuating seawaters, and provides seed sources for reoccurring algal blooms under favorable environmental conditions.     

Relationship between temperature and growth rate of bacterial cultures.

The Arrhenius Law, which was originally proposed to describe the temperature dependence of the specific reaction rate constant in chemical reactions, does not adequately describe the effect of temperature on bacterial growth. Microbiologists have attempted to apply a modified version of this law to bacterial growth by replacing the reaction rate constant by the growth rate constant, but the modified law relationship fits data poorly, as graphs of the logarithm of the growth rate constant against reciprocal absolute temperature result in curves rather than straight lines. Instead, a linear relationship between in square root of growth rate constant (r) and temperature (T), namely, square root = b (T - T0), where b is the regression coefficient and T0 is a hypothetical temperature which is an intrinsic property of the organism, is proposed and found to apply to the growth of a wide range of bacteria. The relationship is also applicable to nucleotide breakdown and to the growth of yeast and molds.     

Regulation of k influx in barley : effects of low temperature

The proteinases present in dark-germinated flax seeds (Linum usitatissimum) were studied as a function of germination at 25°C. A majority of activity was present in basic proteinases with an acidic pH optimum and a temperature optimum of 45°C in the digestion of hemoglobin. Electrophoresis in a sodium dodecyl sulfate-polyacrylamide mixture which had been polymerized with gelatin was used to separate proteins in extracts of seedlings. Subsequent activation of proteinases with Triton X-100 and resultant digestion of gelatin proved to be very reproducible and afforded detection and good quantification of various proteinase zones. An ethylenediaminetetraacetate-sensitive proteinase zone, P4 (about 60,000 daltons), appeared at day 3 after imbibition and attained maximum activity at day 4. This correlates with a rapid loss in vivo of the glyoxysomal enzyme, isocitrate lyase (EC 4.1.3.1). Ethylenediaminetetraacetate also slowed the loss of isocitrate lyase activity in extracts of 4-day seedlings in a dose-dependent manner. The addition of leupeptin, α-tolylsulfonyl fluoride, Pepstatin A, p-chloromercuribenzoate, or 1,10-phenanthroline prior to, during, or after exchange of Triton X-100 for sodium dodecyl sulfate had almost no inhibitory effect upon proteinases in 4-day seedlings.     

Modelling the temperature dependent growth rates of planktic foraminifera

The temperature influence on foraminifera growth rate was analysed using a mechanistic formulation that take into account enzyme inactivation at extreme temperatures. Growth rates are calculated using available published and unpublished laboratory culture experiments for eight species, including Neogloboquadrina pachyderma (sinistral and dextral forms), Neogloboquadrina dutertrei, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinella siphonifera and Orbulina universa. Modeled growth formulas readily reproduce the observed growth patterns for all species. Similar growth patterns are observed for the species that have the same symbiotic algae G. ruber, G. sacculifer, and O. universa. However, different growth patterns are observed for herbivorous species (Neogloboquadrina genus) compared to carnivorous species with or without symbionts. Our growth estimates correspond well to in situ observations from both plankton tows and sediment traps. These estimates will help to improve the quantification of the effects of environmental parameters on foraminifera species distribution and abundance.