| 1. |
- Bååth, Erland, et al.
(author)
-
Temperature Adaptation of Aquatic Bacterial Community Growth Is Faster in Response to Rising than to Falling Temperature
- 2024
-
In: Microbial Ecology. - 0095-3628. ; 87
-
Journal article (peer-reviewed)abstract
- Bacteria are key organisms in energy and nutrient cycles, and predicting the effects of temperature change on bacterial activity is important in assessing global change effects. A changing in situ temperature will affect the temperature adaptation of bacterial growth in lake water, both long term in response to global change, and short term in response to seasonal variations. The rate of adaptation may, however, depend on whether temperature is increasing or decreasing, since bacterial growth and turnover scale with temperature. Temperature adaptation was studied for winter (in situ temperature 2.5 °C) and summer communities (16.5 °C) from a temperate lake in Southern Sweden by exposing them to a temperature treatment gradient between 0 and 30 °C in ~ 5 °C increments. This resulted mainly in a temperature increase for the winter and a decrease for the summer community. Temperature adaptation of bacterial community growth was estimated as leucine incorporation using a temperature Sensitivity Index (SI, log growth at 35 °C/4 °C), where higher values indicate adaptation to higher temperatures. High treatment temperatures resulted in higher SI within days for the winter community, resulting in an expected level of community adaptation within 2 weeks. Adaptation for the summer community was also correlated to treatment temperature, but the rate of adaption was slower. Even after 5 weeks, the bacterial community had not fully adapted to the lowest temperature conditions. Thus, during periods of increasing temperature, the bacterial community will rapidly adapt to function optimally, while decreasing temperature may result in long periods of non-optimal functioning.
|
|
| 2. |
- Campillo-Cora, Claudia, et al.
(author)
-
Bacterial community tolerance to Cu in soils with geochemical baseline concentrations (GBCs) of heavy metals : Importance for pollution induced community tolerance (PICT) determinations using the leucine incorporation method
- 2021
-
In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 155
-
Journal article (peer-reviewed)abstract
- PICT (Pollution Induced Community Tolerance) to Cu is a useful and sensitive tool to assess the effects of Cu pollution in soils under laboratory conditions. However, in field situations, the absence of reference values, i.e. bacterial community tolerance to Cu baseline from non-polluted soils, make the method uncertain when we want to know if a soil is or is not polluted from a microbiological point of view. In order to shed some light on this topic, the PICT (Pollution Induced Community Tolerance) concept was used to determine the bacterial community tolerance to Cu in uncontaminated soils developed on five different parent materials, using log IC50 as a tolerance index. IC50 was calculated as the amount of Cu that inhibit 50% of bacterial growth (estimated via the leucine incorporation method) in a bacterial suspension extracted from soil. With physico-chemical soil characteristics and type of parent material, a linear multiple regression equation was fitted explaining 80% of the variance in log IC50 values. This equation provides a useful tool to estimate the bacterial community tolerance to Cu baseline in a soil using the general soil characteristics, allowing for the more general use of PICT without the need of reference soils.
|
|
| 3. |
- Campillo-Cora, Claudia, et al.
(author)
-
Estimation of baseline levels of bacterial community tolerance to Cr, Ni, Pb, and Zn in unpolluted soils, a background for PICT (pollution-induced community tolerance) determination
- 2022
-
In: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 58:1, s. 49-61
-
Journal article (peer-reviewed)abstract
- The PICT method (pollution-induced community tolerance) can be used to assess whether changes in soil microbial response are due to heavy metal toxicity or not. Microbial community tolerance baseline levels can, however, also change due to variations in soil physicochemical properties. Thirty soil samples (0–20 cm), with geochemical baseline concentrations (GBCs) of heavy metals and from five different parent materials (granite, limestone, schist, amphibolite, and serpentine), were used to estimate baseline levels of bacterial community tolerance to Cr, Ni, Pb, and Zn using the leucine incorporation method. General equations (n = 30) were determined by multiple linear regression using general soil properties and parent material as binary variables, explaining 38% of the variance in log IC50 (concentration that inhibits 50% of bacterial growth) values for Zn, with 36% for Pb, 44% for Cr, and 68% for Ni. The use of individual equations for each parent material increased the explained variance for all heavy metals, but the presence of a low number of samples (n = 6) lead to low robustness. Generally, clay content and dissolved organic C (DOC) were the main variables explaining bacterial community tolerance for the tested heavy metals. Our results suggest that these equations may permit applying the PICT method with Zn and Pb when there are no reference soils, while more data are needed before using this concept for Ni and Cr.
|
|
| 4. |
- Fernández-Calviño, David, et al.
(author)
-
Isothiazolinone inhibition of soil microbial activity persists despite biocide dissipation
- 2023
-
In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 178
-
Journal article (peer-reviewed)abstract
- Soil microbial growth and activity are generally assumed to recover rapidly after dissipation of organic toxicants. We studied the effects of four readily degradable isothiazolinone biocides (benzisothiazolinone, BIT; methylisothiazolinone, MIT; octylisothiazolinone, OIT; 4,5-dichloro-2-octyl-isothiazolinone, DCOIT) on bacterial growth, fungal growth, basal respiration, and substrate-induced respiration in controlled soil microcosm experiments. Bacterial growth followed by fungal growth were the two most sensitive endpoints during the first two days. Significant dissipation of biocides occurred within just 8 h and 94–100% had dissipated after 40 days except for DCOIT tested at a high concentration (50 mg kg−1, 54% remaining after 40 d). Despite biocide dissipation, all isothiazolinones inhibited bacterial growth for >7 days, whereas fungal growth and substrate-induced respiration were inhibited for up to 40 days. Bacterial growth recovery after 40 days was linked to development of bacterial community tolerance for DCOIT, but not for the other less persistent isothiazolinones. Our study is the first to report on toxic effects of isothiazolinones on soil microbial growth and demonstrates that inhibitory effects of isothiazolinones on soil microbial growth and activity (especially fungal growth and substrate-induced respiration) persisted even long after biocide dissipation, indicating “legacy effects” and retarded recovery of soil microbial functions. We propose that retarded recovery of fungal, relative to bacterial, growth may be a general phenomenon during the dissipation of toxicants in contaminated soils and that it may be explained by intrinsic differences between bacterial and fungal biology in soil and by competitive interactions between these two dominant groups of soil microbial decomposers.
|
|
| 5. |
- Fernández-Calviño, David, et al.
(author)
-
Short-term toxicity assessment of a triazine herbicide (terbutryn) underestimates the sensitivity of soil microorganisms
- 2021
-
In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 154
-
Journal article (peer-reviewed)abstract
- Little is known about the impacts of persistent triazine herbicides and biocides on soil microorganisms. Terbutryn toxicity in soil microorganisms was studied using bacterial and fungal growth, substrate induced respiration (SIR) and basal respiration as ecotoxicological end-points. In the short-term (0–7 days), increasing concentrations of terbutryn (0–800 mg kg−1) progressively inhibited bacterial and fungal growth by up to 33–36% (4 h) and 49–55% (7 days), whereas SIR and basal soil respiration remained unaffected. Following long-term (40 days) exposure to terbutryn, both bacterial and fungal growth were inhibited by up to 76–78%, and SIR was inhibited by up to 53%. Hence, our results unexpectedly demonstrate time-cumulative microbial growth inhibition over extended time periods in soil and indicate that current ecotoxicological guidelines may underestimate risks posed by chemicals to soil microorganisms.
|
|
| 6. |
- Kritzberg, Emma, et al.
(author)
-
Seasonal variation in temperature sensitivity of bacterial growth in a temperate soil and lake
- 2022
-
In: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941. ; 98:10
-
Journal article (peer-reviewed)abstract
- Faster bacterial biomass turnover is expected in water compared to soil, which would result in more rapid community adaption to changing environmental conditions, including temperature. Bacterial community adaptation for growth is therefore predicted to have larger seasonal amplitudes in lakes than in soil. To test this prediction, we compared the seasonal variation in temperature adaptation of bacterial community growth in a soil and lake in Southern Sweden (Tin situ 0-20°C, mean 10°C) during 1.5 years, based on monthly samplings including two winters and summers. An indicator of community adaptation, minimum temperature for growth (Tmin), was calculated from bacterial growth measurements (Leu incorporation) using the Ratkowsky model. The seasonal variation in Tmin (sinusoidal function, R2 = 0.71) was most pronounced for the lake bacterial community, with an amplitude for Tmin of 3.0°C (-4.5 to -10.5°C) compared to 0.6°C (-7 to -8°C) for the soil. Thus, Tmin in water increased by 0.32°C/degree change of Tin situ. Similar differences were also found when comparing four lakes and soils in the winter and summer (amplitudes 2.9°C and 0.9°C for lakes and soils, respectively). Thus, seasonal variation in temperature adaptation has to be taken into account in lakes, while for soils a constant Tmin can be used.
|
|
| 7. |
- Leizeaga, Ainara, et al.
(author)
-
Repeated drying and rewetting cycles accelerate bacterial growth recovery after rewetting
- 2022
-
In: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 58:4, s. 365-374
-
Journal article (peer-reviewed)abstract
- Two patterns of bacterial growth response upon drying and rewetting (DRW) of soils have previously been identified. Bacterial growth can either start increasing immediately after rewetting in a linear fashion (“type 1” response) or start increasing exponentially after a lag period (“type 2” response). The effect of repeated DRW cycles was studied in three soils with different response patterns after a single DRW cycle (“type 1”, “type 2” with a short lag period and “type 2” with a long lag period). The soils were exposed to seven DRW cycles, and respiration and bacterial growth were monitored after 1, 2, 3, 5, and 7 cycles. Exposure to repeated DRW shifted the bacterial growth response from a “type 2” to a “type 1” pattern, resulting in an accelerated growth recovery to a pre-disturbance growth rate. Bacterial growth in soils that initially had a “type 1” response also tended to recover faster after each subsequent DRW cycle. The respiration patterns after DRW also indicated the same transition from a “type 2” to a “type 1” pattern. Our results show that exposure to repeated DRW cycles will shape the bacterial response to future DRW cycles, which might be mediated by a shift in species composition, a physiological adjustment, evolutionary changes, or a combination of the three.
|
|
| 8. |
- Lekberg, Ylva, et al.
(author)
-
Fatty acid 16:1ω5 as a proxy for arbuscular mycorrhizal fungal biomass : current challenges and ways forward
- 2022
-
In: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 58:8, s. 835-842
-
Journal article (peer-reviewed)abstract
- Fatty acid biomarkers have emerged as a useful tool to quantify biomass of various microbial groups. Here we focus on the frequent use of the fatty acid 16:1ω5 as a biomarker for arbuscular mycorrhizal (AM) fungi in soils. We highlight some issues with current applications of this method and use several examples from the literature to show that the phospholipid fatty acid (PLFA) 16:1ω5 can occur in high concentrations in soils where actively growing AM fungi are absent. Unless the study includes a control where the contribution of other microbes can be estimated, we advocate for the use of the neutral lipid fatty acid (NLFA) 16:1ω5. This biomarker has higher specificity, is more responsive to shifts in AM fungal biomass, and quantification can be conducted along with PLFA analysis without doubling analytical efforts. We conclude by contrasting various methods used to measure AM fungal biomass in soil and highlight future research needs to optimize fatty acid analyses.
|
|
| 9. |
- Li, Jinquan, et al.
(author)
-
Temperature adaptation of soil microbial respiration in alpine, boreal and tropical soils : An application of the square root (Ratkowsky) model
- 2021
-
In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 27:6, s. 1281-1292
-
Journal article (peer-reviewed)abstract
- Warming is expected to stimulate soil microbial respiration triggering a positive soil carbon-climate feedback loop while a consensus remains elusive regarding the magnitude of this feedback. This is partly due to our limited understanding of the temperature-adaptive response of soil microbial respiration, especially over broad climatic scales. We used the square root (Ratkowsky) model to calculate the minimum temperature for soil microbial respiration (Tmin, which describes the temperature adaptation of soil microbial respiration) of 298 soil samples from alpine grasslands on the Tibetan Plateau and forest ecosystems across China with a mean annual temperature (MAT) range from −6°C to +25°C. The instantaneous soil microbial respiration was determined between 4°C and 28°C. The square root model could well fit the temperature effect on soil microbial respiration for each individual soil, with R2 higher than 0.98 for all soils. Tmin ranged from −8.1°C to −0.1°C and increased linearly with increasing MAT (R2 = 0.68). MAT dominantly regulated Tmin variation when accounting simultaneously for multiple other drivers (mean annual precipitation, soil pH and carbon quality); an independent experiment showed that carbon availability had no significant effect on Tmin. Using the relationship between Tmin and MAT, soil microbial respiration after an increased MAT could be estimated, resulting in a relative increase in respiration with decreasing MAT. Thus, soil microbial respiration responses are adapted to long-term temperature differences in MAT. We suggest that Tmin = −5 + 0.2 × MAT, that is, every 1°C rise in MAT is estimated to increase Tmin of respiration by approximately 0.2°C, could be used as a first approximation to incorporate temperature adaptation of soil microbial respiration in model predictions. Our results can be used to predict future changes in the response of soil microbial respiration to temperature over different levels of warming and across broad geographic scales with different MAT.
|
|
| 10. |
- Nottingham, Andrew T., et al.
(author)
-
Microbial diversity declines in warmed tropical soil and respiration rise exceed predictions as communities adapt
- 2022
-
In: Nature Microbiology. - : Springer Science and Business Media LLC. - 2058-5276. ; 7:10, s. 1650-1660
-
Journal article (peer-reviewed)abstract
- Perturbation of soil microbial communities by rising temperatures could have important consequences for biodiversity and future climate, particularly in tropical forests where high biological diversity coincides with a vast store of soil carbon. We carried out a 2-year in situ soil warming experiment in a tropical forest in Panama and found large changes in the soil microbial community and its growth sensitivity, which did not fully explain observed large increases in CO2 emission. Microbial diversity, especially of bacteria, declined markedly with 3 to 8 °C warming, demonstrating a breakdown in the positive temperature-diversity relationship observed elsewhere. The microbial community composition shifted with warming, with many taxa no longer detected and others enriched, including thermophilic taxa. This community shift resulted in community adaptation of growth to warmer temperatures, which we used to predict changes in soil CO2 emissions. However, the in situ CO2 emissions exceeded our model predictions threefold, potentially driven by abiotic acceleration of enzymatic activity. Our results suggest that warming of tropical forests will have rapid, detrimental consequences both for soil microbial biodiversity and future climate.
|
|
