Comparative Toxicities of Salts on Microbial Processes in Soil

ABSTRACTSoil salinization is a growing threat to global agriculture and carbon sequestration, but to date it remains unclear how microbial processes will respond. We studied the acute response to salt exposure of a range of anabolic and catabolic microbial processes, including bacterial (leucine incorporation) and fungal (acetate incorporation into ergosterol) growth rates, respiration, and gross N mineralization and nitrification rates. To distinguish effects of specific ions from those of overall ionic strength, we compared the addition of four salts frequently associated with soil salinization (NaCl, KCl, Na2SO4, and K2SO4) to a nonsaline soil. To compare the tolerance of different microbial processes to salt and to interrelate the toxicity of different salts, concentration-response relationships were established. Growth-based measurements revealed that fungi were more resistant to salt exposure than bacteria. Effects by salt on C and N mineralization were indistinguishable, and in contrast to previous studies, nitrification was not found to be more sensitive to salt exposure than other microbial processes. The ion-specific toxicity of certain salts could be observed only for respiration, which was less inhibited by salts containing SO42−than Cl−salts, in contrast to the microbial growth assessments. This suggested that the inhibition of microbial growth was explained solely by total ionic strength, while ion-specific toxicity also should be considered for effects on microbial decomposition. This difference resulted in an apparent reduction of microbial growth efficiency in response to exposure to SO42−salts but not to Cl−salts; no evidence was found to distinguish K+and Na+salts.

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Digestion in defaunated and refaunated sheep fed soybean oil hydrolysate or crushed toasted soybeans

Netherlands Journal of Agricultural Science ◽

10.18174/njas.v41i3.620 ◽

1993 ◽

Vol 41 (3) ◽

pp. 205-219

Author(s):

C.J. Van Nevel ◽

S. De Smet ◽

D.I. Demeyer

Keyword(s):

Total Lipid ◽

Microbial Growth ◽

Intestinal Tract ◽

Growth Efficiency ◽

Minor Effect ◽

Molar Percentage ◽

Rumen Metabolism ◽

Fermentation Pattern ◽

A Minor ◽

Microbial Growth Efficiency

Defaunated then refaunated sheep were given diets containing soyabean oil hydrolysate (SOH: 70 g/day) or an equivalent amount of lipids administered as crushed toasted soyabeans (TSB). Defaunation increased molar percentage of propionate in the rumen, while butyrate decreased. SOH caused a similar effect in both the defaunated and refaunated rumen, while the effect on acetate proportions was variable. Protozoal counts were lower after feeding SOH. Crushed toasted soyabeans had a minor effect on rumen fermentation pattern. Rumen digestibility of organic matter was decreased by both defaunation and SOH feeding, with a concomitant shift in digestion to the lower intestinal tract. Total tract digestibility was not affected. Both treatments increased nonammonia N flows at the duodenum, but this was only significant with defaunation. Total tract digestion of N remained almost constant. Defaunation resulted in more microbial protein reaching the duodenum. Except for the TSB diet, total lipid leaving the rumen equalled intake. Total tract digestibility of total lipid was much higher with SOH and TSB than with controls. Defaunation almost doubled microbial growth efficiency and this value tended to increase by SOH feeding. The decrease of protozoal count or even elimination of protozoa after lipid feeding could not entirely explain the change in rumen metabolism, as additional changes in defaunated sheep were shown.

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Gas balance method for testing of microbial growth efficiency after carbon substrate pulse

Acta Biotechnologica ◽

10.1002/abio.370060206 ◽

1986 ◽

Vol 6 (2) ◽

pp. 123-128 ◽

Cited By ~ 8

Author(s):

L. A. Baburin ◽

I. E. Shvinka ◽

M. P. Ruklisha ◽

U. E. Viesturs

Keyword(s):

Microbial Growth ◽

Growth Efficiency ◽

Balance Method ◽

Carbon Substrate ◽

Microbial Growth Efficiency ◽

Gas Balance

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Do microbial communities adapt to the temperature of their climate?

10.5194/egusphere-egu2020-776 ◽

2020 ◽

Author(s):

Daniel Tajmel ◽

Carla Cruz Paredes ◽

Johannes Rousk

Keyword(s):

Environmental Factors ◽

Microbial Communities ◽

Large Scale ◽

Microbial Growth ◽

Environmental Temperature ◽

Microbial Processes ◽

Temperature Relationship ◽

Maximum Temperature ◽

Mean Annual Temperature ◽

The Impact

Terrestrial biogeochemical cycles are regulated by soil microorganisms. The microbial carbon release due to respiration and carbon sequestration through microbial growth determine whether soils become sources or sinks for carbon. Temperature i&#8203;s one of the most important environmental factors controlling both microbial growth and respiration. Therefore, to understand the influence of temperature on microbial processes is crucial. One strategy to predict how ecosystems will respond to warming is to use geographical ecosystem differences, in space-for-time (SFT) substitution approaches. We hypothesized (1) that microbes should be adapted to their environmental temperature leading to microbial communities with warm-shifted temperature relationships in warmer environments, and vice versa. Furthermore, we hypothesized&#160; (2) that other factors should not influence microbial temperature relationships, and (3) that the temperature sensitivity of microbial processes (Q10) should be linked to the microbial temperature relationships.&#160;In this project, we investigated the effects of environmental temperature on microbial temperature relationships for microbial growth and respiration along a natural climate gradient along a transect across Europe to predict the impact of a warming climate. The transect was characterized by mean annual temperature (MAT) ranging from - 4 degrees Celsius (Greenland) to 18 degrees Celsius (Southern Spain), while other environmental factor ranges were broad and unrelated to climate, including pH from 4.0 to 8.8, C/N ratio from 7 to 50, SOM from 4% to 94% and plant communities ranging from arctic tundra to Mediterranean grasslands. More than 56 soil samples were analyzed and microbial temperature relationships were determined using controlled short-term laboratory incubations from 0 degrees Celsius to 45 degrees Celsius. The link between microbial temperature relationship and the climate was assessed by using the relationship between the environmental temperature and indices for microbial temperature relationships including the minimum (Tmin), optimum (Topt) and maximum temperature (Tmax) for microbial growth as well as for respiration. To estimate the Tmin, Topt&#160;and Tmax&#160;the square root equation, the Ratkowsky model was used.&#160;We found that microbial communities were adapted to their environmental temperature. The microbial temperature relationship was stronger for microbial growth than for respiration. For 1 degrees Celsius rise in MAT, Tmin increased 0.22 degrees Celsius for bacterial and 0.28 degrees Celsius for fungal growth, while Tmin for respiration increased by 0.16 per 1 degrees Celsius rise. Tmin&#160;was also found to be universally linked to Q10, such that higher Tmin resulted in higher Q10. Other environmental factors (pH, C/N ratio, SOM, vegetation cover) did not influence the temperature relationships. By incorporating the determined relationships between environmental temperature and microbial growth and respiration into large scale ecosystem models, we can get a better understanding of the influence of microbial adaptation to warmer climate on the C-exchange between soils and atmosphere.

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Effect of Phenylalanine and Its Metabolites on the Metabolism of Leucocytes and Lymphocytes

Clinical Science ◽

10.1042/cs0490343 ◽

1975 ◽

Vol 49 (4) ◽

pp. 343-351

Author(s):

D. M. Bradley ◽

R. F. Mahler

Keyword(s):

Leucine Incorporation ◽

Published Data ◽

Suitable Model ◽

Acetate Incorporation ◽

Inborn Errors ◽

Insoluble Material ◽

Model Cell ◽

Resting Lymphocytes ◽

Citrate Synthetase

1. The pathogenesis of the mental retardation in phenylketonuria remains obscure. Leucocytes have proved of value in the study of other inborn errors of metabolism. The lymphocyte is a suitable model cell for the study of mammalian metabolism, because of its ability to divide in vitro in response to various stimuli. 2. We have examined the effects of phenylalanine, phenylpyruvate, phenyl-lactate and phenylacetate on the human leucocyte and the resting and phyto-haemagglutinin-stimulated rabbit lymphocyte. 3. Phenylpyruvate and phenyl-lactate reduced acetate incorporation into leucocyte lipid by 38% and 48% respectively. Only phenyl-lactate reduced acetate incorporation into the resting and stimulated lymphocyte, by 20% and 34% respectively. 4. Glucose incorporation into leucocyte lipid was unaffected by phenylalanine, phenylpyruvate and phenyl-lactate. Only phenyl-lactate inhibited (46%) the production of CO2 from glucose. 5. Phenylalanine and leucine incorporation into trichloroacetic acid-insoluble material of resting and stimulated lymphocytes was inhibited by phenyl-lactate (10–42%), phenylpyruvate (27–57%) and phenylacetate (19–39%). 6. Uridine incorporation into resting and stimulated cells was inhibited by phenyl-lactate (22–26%), phenylpyruvate (42–52%) and phenylacetate (20%). 7. Thymidine incorporation into resting lymphocytes was reduced by phenyl-lactate, phenylpyruvate, phenylacetate and phenylalanine by 12–26%. Incorporation into the stimulated cell was inhibited by phenylpyruvate and phenyl-lactate (90%) and phenylacetate (66%). 8. Phenylalanine inhibited lymphocyte pyruvate kinase and phenylpyruvate inhibited citrate synthetase. 9. These results are compared with published data relating to experimental hyperphenylalaninaemia and the effects of these metabolites on nervous tissue in vitro.

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Limitation of Bacterial Growth by Dissolved Organic Matter and Iron in the Southern Ocean

Applied and Environmental Microbiology ◽

10.1128/aem.66.2.455-466.2000 ◽

2000 ◽

Vol 66 (2) ◽

pp. 455-466 ◽

Cited By ~ 127

Author(s):

Matthew J. Church ◽

David A. Hutchins ◽

Hugh W. Ducklow

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Southern Ocean ◽

Bacterial Growth ◽

Bacterial Biomass ◽

Biomass Accumulation ◽

Growth Efficiency ◽

Bacterial Growth Efficiency ◽

Leucine Incorporation ◽

Mean Cell Volume

ABSTRACT The importance of resource limitation in controlling bacterial growth in the high-nutrient, low-chlorophyll (HNLC) region of the Southern Ocean was experimentally determined during February and March 1998. Organic- and inorganic-nutrient enrichment experiments were performed between 42°S and 55°S along 141°E. Bacterial abundance, mean cell volume, and [3H]thymidine and [3H]leucine incorporation were measured during 4- to 5-day incubations. Bacterial biomass, production, and rates of growth all responded to organic enrichments in three of the four experiments. These results indicate that bacterial growth was constrained primarily by the availability of dissolved organic matter. Bacterial growth in the subtropical front, subantarctic zone, and subantarctic front responded most favorably to additions of dissolved free amino acids or glucose plus ammonium. Bacterial growth in these regions may be limited by input of both organic matter and reduced nitrogen. Unlike similar experimental results in other HNLC regions (subarctic and equatorial Pacific), growth stimulation of bacteria in the Southern Ocean resulted in significant biomass accumulation, apparently by stimulating bacterial growth in excess of removal processes. Bacterial growth was relatively unchanged by additions of iron alone; however, additions of glucose plus iron resulted in substantial increases in rates of bacterial growth and biomass accumulation. These results imply that bacterial growth efficiency and nitrogen utilization may be partly constrained by iron availability in the HNLC Southern Ocean.

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Heavy and wet: The consequences of violating assumptions of measuring soil microbial growth efficiency using the 18O water method

Elem Sci Anth ◽

10.1525/elementa.069 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Grace Pold ◽

Luiz A. Domeignoz-Horta ◽

Kristen M. DeAngelis

Keyword(s):

Microbial Community ◽

Microbial Communities ◽

Microbial Growth ◽

Microbial Community Composition ◽

Soil Microbial Communities ◽

Growth Efficiency ◽

Experimental Conditions ◽

Soil Microbial ◽

Use Efficiency ◽

Microbial Growth Efficiency

Soils store more carbon than the biosphere and atmosphere combined, and the efficiency to which soil microorganisms allocate carbon to growth rather than respiration is increasingly considered a proxy for the soil capacity to store carbon. This carbon use efficiency (CUE) is measured via different methods, and more recently, the 18O-H2O method has been embraced as a significant improvement for measuring CUE of soil microbial communities. Based on extrapolating 18O incorporation into DNA to new biomass, this measurement makes various implicit assumptions about the microbial community at hand. Here we conducted a literature review to evaluate how viable these assumptions are and then developed a mathematical model to test how violating them affects estimates of the growth component of CUE in soil. We applied this model to previously collected data from two kinds of soil microbial communities. By changing one parameter at a time, we confirmed our previous observation that CUE was reduced by fungal removal. Our results also show that depending on the microbial community composition, there can be substantial discrepancies between estimated and true microbial growth. Of the numerous implicit assumptions that might be violated, not accounting for the contribution of sources of oxygen other than extracellular water to DNA leads to a consistent underestimation of CUE. We present a framework that allows researchers to evaluate how their experimental conditions may influence their 18O-H2O-based CUE measurements and suggest the parameters that need further constraining to more accurately quantify growth and CUE.

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Limiting factors for soil microbial growth in climate change simulation treatments in the Subarctic

10.5194/egusphere-egu2020-5352 ◽

2020 ◽

Author(s):

Mingyue Yuan ◽

Meng Na ◽

Lettice Hicks ◽

Johannes Rousk

Keyword(s):

Climate Change ◽

Bacterial Growth ◽

N Mineralization ◽

Microbial Growth ◽

Fungal Growth ◽

Plant Productivity ◽

Limiting Factors ◽

Limiting Factor ◽

Soil Microbial ◽

C Limitation

Soil microorganisms play a crucial role in the regulation of nutrient cycling, and are thought to be either limited by low nutrient availability, or by labile carbon supplied by nutrient limited plant productivity. It remains unknown how climate change will affect the rate-limiting resources for decomposer microorganisms in the Arctic, rendering feedbacks to climate change highly uncertain. In this study, we focused on the responses of soil microbial community processes to simulated climate change in a subarctic tundra system in Abisko, Sweden, using litter additions to represent arctic greening and inorganic N fertilizer additions to represent a faster nutrient cycling due to arctic warming. We hypothesized that 1) the plant community would shift and plant productivity would increase in response to N fertilization, 2) microbial process rates would be stimulated by both plant litter and fertilizer additions, and 3) the growth limiting factors for decomposer microorganisms would shift toward nutrient limitation in response to higher plant material input, and towards C-limitation in response to N-fertilizer additions.&#160;We assessed the responses of the plant community composition (vegetation surveys) and productivity (NDVI), microbial processes (bacterial growth, fungal growth, C and N mineralization) along with an assessment of the limiting factors for fungal and bacterial growth. The growth-limiting factors were determined by full factorial additions of nutrients (C, N, P), with measurement of microbial growth and respiration following brief incubations in the laboratory. We found that plant productivity was ca. 15% higher in the N fertilized plots. However, field-treatments had limited effects on bacterial growth, fungal growth and the fungal-to-bacterial growth ratio in soils. Field-treatments also had no significant effect on the rate of soil C mineralization, but did affect rates of gross N mineralization. Gross N mineralization was twice as high in N fertilized plots compared to the control. In control soils, bacterial growth increased 4-fold in response to C, indicating that bacterial growth was C limited. Bacterial growth remained C limited in soils from all field-treatments. However, in the N fertilized soils, the C limitation was 1.8-times greater than the control, while in soils with litter input, the C limitation was 0.83-times the control, suggesting that the N fertilized soils were moving towards stronger C-limitation and the litter addition soils were becoming less C-limited. The limiting factor for fungal growth was difficult to resolve. We presumed that the competition of fungi with bacteria decreased our resolution to detect the limiting factor. Therefore, factorial nutrient addition were combined with low amount of bacterial specific inhibitors.

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