| 1. |
- Bárcenas-Moreno, Gema, et al.
(författare)
-
Functional implications of the pH-trait distribution of the microbial community in a re-inoculation experiment across a pH gradient
- 2016
-
Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 93, s. 69-78
-
Tidskriftsartikel (refereegranskat)abstract
- We compared the influence of the microbial community composition and the environmental conditions for the functioning - microbial growth and respiration - and trait distribution - bacterial pH tolerance - of soil microorganisms across a pH gradient. Sterilised soil microcosms, including pH 4.1, 5.2, 6.7 and 8.3, with added plant litter were inoculated with unsterilized soil in a factorial design and monitored during two months. The trait distribution - pH-tolerance - of bacterial communities converged with the pH of the soil environment. Still, the different inoculum communities could result in suboptimal pH-tolerance in all soil pH environments; inoculum communities derived from low pHs had lower than optimal pH-tolerance in high soil pH environments, and vice versa. The functioning of bacterial communities with trait distributions mismatched to the soil pH environment was impaired. The legacy of the initial bacterial trait distribution on bacterial pH tolerance and functioning was detected within one week and remained for two months in all soil pH environments. Fungal inoculum communities derived from low compared to high pHs resulted in higher fungal functioning. Thus, in contrast with bacteria there was no evidence that variation in pH-tolerance influenced fungal performance. Instead the fungal inoculum size appeared to explain these results. Bacteria dominated respiration in high pH while fungi dominated at low pH environments. Consequently, respiration was affected by how well-matched the bacterial trait distribution was to the pH of the soil environment at higher pHs. At low pH, the inoculum size of fungi appeared to determine the respiration.
|
|
| 2. |
- Bååth, Erland, et al.
(författare)
-
pH Tolerance in Freshwater Bacterioplankton: Trait-Variation of the Community measured by Leucine Incorporation.
- 2015
-
Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 81:21, s. 7411-7419
-
Tidskriftsartikel (refereegranskat)abstract
- pH is an important factor determining bacterial community composition in soil and water. We have directly determined the community tolerance (trait variation) to pH in communities from 22 lakes and streams ranging in pH from 4 to 9 using a growth based method not relying on distinguishing between individual populations. pH in the water samples was altered to up to 16 pH values, covering in situ pH ± 2.5 units, and the tolerance was assessed by measuring bacterial growth (Leu incorporation) instantaneously after pH adjustment. The resulting unimodal response curves, reflecting community tolerance to pH, were well modeled with a double logistic equation (mean R(2) = 0.97). Optimal pH for growth (pHopt) among the bacterial communities was closely correlated with in situ pH, with a slope (0.89 ± 0.099) close to unity. The pH interval, in which growth was ≥90 % of that at pHopt, was 1.1 to 3 pH units wide (mean 2.0 pH units). Tolerance response curves of communities originating from circum-neutral pH were symmetrical, while in high (pH 8.9) and especially low pH waters (pH<5.5) asymmetric tolerance curves were found. In low pH waters decreasing pH was more detrimental for bacterial growth than increasing pH, with a tendency for the opposite for high pH waters. A pH tolerance index, using the ratio of growth at only two pH values (pH 4 and 8), was closely related to pHopt (R(2) = 0.83), allowing for easy determination of pH tolerance during rapid changes in pH.
|
|
| 3. |
- Fernández-Calviño, David, et al.
(författare)
-
Ecotoxicological assessment of propiconazole using soil bacterial and fungal growth assays
- 2017
-
Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 115, s. 27-30
-
Tidskriftsartikel (refereegranskat)abstract
- Effects of the fungicide propiconazole on soil microorganisms were tested using [3H] leucine incorporation and [14C] acetate in ergosterol incorporation to measure bacterial and fungal growth inhibition, respectively. Growth was compared to basal respiration (BR) and substrate-induced respiration (SIR) in soil microcosms established according to the OECD 217 guideline. Fungal growth was most sensitive with IC50 values remaining around 300 mg kg−1 during 40 days of incubation. SIR was initially less sensitive (IC50 1300 mg kg−1), but IC50 values progressively decreased over time to reach 380 mg kg−1 after 40 days. Bacterial growth was affected at concentrations ≥200 mg kg−1, but exhibited more complex dose-response relationships possibly due to a combination of direct toxicity, bacterial community adaptation, and competitive release from the more severely affected fungi. BR was either stimulated or not affected by propiconazole. Our results indicate that group-specific endpoints targeting microbial growth will improve ecotoxicological assessment of toxicants for environmental risk assessment.
|
|
| 4. |
- Fernández-Calviño, David, et al.
(författare)
-
Interaction between pH and Cu toxicity on fungal and bacterial performance in soil
- 2016
-
Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 96, s. 20-29
-
Tidskriftsartikel (refereegranskat)abstract
- pH is an important parameter affecting heavy metal toxicity in soil. Bacterial and fungal growth, and respiration, during 60 days were determined in response to Cu additions (up to 32 mmol Cu kg-1 soil) in four soils with pH varying between 4.5 and 7.8. We hypothesized that at higher pH the toxic effect of Cu would decrease. In soil with pH 7.8, no negative effects on microbial growth were found up to 32 mmol Cu kg-1 soil. In soils with pH 4.5, 5.5 and 6.9, increasing Cu initially resulted in decreasing bacterial growth and respiration, but with similar responses in all three soils. In these soils bacterial growth was the most sensitive microbial variable after 2 days, with 34-59% inhibition at 2 mmol Cu kg-1, and almost total inhibition at 16 mmol Cu kg-1 and above. Respiration was only inhibited to 32-67% at 16 mmol Cu kg-1. Bacterial growth recovered over time in soils with pH 4.5 and 5.5 and with 8 and 16 mmol Cu kg-1, resulting in no clear dose-response relationship. Soil respiration did not recover to levels in the unpolluted control. Fungal growth was not negatively affected by the Cu addition in short-term and even increased at high Cu levels. The Pollution Induced Community Tolerance (PICT) of the bacterial community to Cu increased with Cu level in soils with pH 4.5, 5.5 and 6.9, with effects already at 2-4 mmol Cu kg-1, while in the soil pH 7.8 only a small increase in PICT was found at 32 mmol Cu kg-1. PICT was closely correlated to the bacterial growth inhibition measured 2 days after Cu additions, suggesting that the PICT increase was mainly due to initial survival of tolerant bacteria. PICT was also closely correlated to water soluble Cu concentrations. High pH thus mitigated the toxic effect of Cu; this warrant pH to be included in decisions on limit values for Cu toxicity in soil.
|
|
| 5. |
- Frossard, Aline, et al.
(författare)
-
Long- and short-term effects of mercury pollution on the soil microbiome
- 2018
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 120, s. 191-199
-
Tidskriftsartikel (refereegranskat)abstract
- Despite the toxicity of mercury (Hg) for organisms in the environment, little is known on its impact on the soil microbiome, especially its chronic effect. Here, we assessed the effects of a long-term contamination of Hg in soils on the bacterial and fungal communities along a gradient of contamination from no to high contamination. Short-term reactions (30 days) of the microbial communities in these soils having different levels of historic Hg contamination were further evaluated in microcosm experiments where soils were either spiked with dissolved HgCl2 or not. Results show a clear impact of a long-term Hg contamination on both bacterial and fungal community structures and diversity but only a weak effect was observed on their activities (basal respiration and growth rates). No short-term effects of Hg were observed on the microbial community structures and activities. Taxa from the Chthoniobacteraceae (bacteria) and Trichosporon sp. (fungi) were associated with high Hg contaminated soils, implying they possess capabilities to tolerate Hg in soils. Abundance of mercury reductase (merA) gene copies increased with higher Hg concentrations in soils both during short and long-term exposure to Hg pointing to potential mechanisms within microbial cells to tolerate higher amounts of Hg in soils.
|
|
| 6. |
- KAMBLE, Pramod N., et al.
(författare)
-
Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil
- 2018
-
Ingår i: Pedosphere. - 1002-0160. ; 28:2, s. 255-260
-
Tidskriftsartikel (refereegranskat)abstract
- Microbial growth in soil is mostly limited by lack of carbon (C). However, adding fresh, C-rich litter can induce nitrogen (N) limitation. We studied the effect of alleviating C and N limitation in high-pH (> 8) soils, soils expected to favor bacterial over fungal growth. Nitrogen limitation was induced by incubating soils amended with C-rich substrate (starch or straw) for 4 weeks. Limiting nutrients and the effects of alleviating limitation were then studied by adding C (as glucose) or N (as NH4NO3) and measuring microbial growth and respiration after 4 d. In non-amended, C-limited soils, adding C but not N increased both microbial respiration and bacterial growth. In N-limited, substrate-amended soils, adding C increased respiration, whereas adding N increased both microbial respiration and growth. Inducing N limitation by amending with straw was most easily detected in increased fungal growth after the addition of N, whereas with starch, only bacterial growth responded to alleviating N limitation. Compared to earlier results using a low-pH soil, the effect of substrate used to induce N limitation was more important than pH for inducing bacterial or fungal growth after alleviating N limitation. Furthermore, we found no evidence that alleviating N limitation resulted in decreased respiration concomitant with increased microbial growth in soil, suggesting no drastic changes in C use efficiency.
|
|
| 7. |
- Kamble, Pramod N., et al.
(författare)
-
Comparison of fungal and bacterial growth after alleviating induced N-limitation in soil
- 2016
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 103, s. 97-105
-
Tidskriftsartikel (refereegranskat)abstract
- The extent and type of nutrient limitation will affect soil microorganism activity and may change the balance between organism groups, like fungi and bacteria. Limiting nutrients have traditionally been measured as increased respiration after adding nutrients, but this will not differentiate between fungal or bacterial responses. We compared respiration, bacterial and fungal growth after alleviating limitation in soils originally being C-limited, but experimentally altered to N-limitation. Three soils of similar pH and organic matter but with different N availability were used. We amended the soils with C-rich substrates, starch (40 mg g−1) and straw (80 mg g−1), followed by a 4 weeks incubation at 22 °C to induce N-limitation. Starch amendment resulted in increased respiration and bacterial growth, while straw amendment increased all three variables (respiration, bacterial and fungal growth), with only minor differences between soils. Alleviating C- and N-limitation was then tested in a short-term assay after adding C (glucose) and NH4NO3 in a full factorial design. In non-amended, C-limited soils, adding C resulted in increased respiration and especially bacterial growth, while fungal growth only increased in the High N soil. Straw amendment resulted in N-limitation, since adding N increased respiration and especially fungal growth. N-limitation for bacterial growth was evident in all starch amended soils, with similar effects for respiration, although adding C also increased respiration. Fungal growth was not affected by C- or N-additions in starch-amended soils. Thus, which microbial group that responded to alleviating N-limitation depended on the C-source in the soil. Furthermore, we found no indication of growth and respiration reacting differently to alleviating N-limitation indicating altered C-use efficiency.
|
|
| 8. |
- Kolb, Gundula S., et al.
(författare)
-
Effects of Nesting Cormorants (Phalacrocorax carbo) on Soil Chemistry, Microbial Communities and Soil Fauna
- 2015
-
Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 18:4, s. 643-657
-
Tidskriftsartikel (refereegranskat)abstract
- Seabirds act as vectors transporting marine nutrients to land by feeding on fish while nesting and roosting on islands. By depositing large amounts of nutrient-rich guano on their nesting islands they strongly affect island soils, vegetation and consumers. However, few studies have investigated how nesting seabirds affect soil communities. In this study, we investigated how cormorant nesting colonies affect soil chemistry, soil microbes and soil and litter fauna on their nesting islands in the Stockholm archipelago, Sweden. We found that cormorant colonies strongly increase organic soil N and P concentrations, and the effect is stronger close to cormorant nests. Microbial communities were studied by extracting phospholipid fatty acids (PLFA) from the soil. The total amounts of PLFA and the amount of PLFA indicating bacterial biomass were lower on active cormorant islands than on reference islands. Furthermore, PLFA structure and thus microbial community structure differed between cormorant and reference islands. Among ten investigated soil and litter arthropod groups three groups (Thysanoptera, Araneae and Oribatida) showed lower densities and one group (Astigmata) showed higher densities in soils on active cormorant than on reference islands. Some arthropod groups showed strong spatial variation on the cormorant islands. Astigmata, Mesostigmata and Diptera showed higher densities in soil samples close to cormorant nests, whereas Oribatida, Collembola and Hemiptera showed lower densities in litter samples close to cormorant nests than in samples taken 3-20 m away from nests. Overall, the cormorant colonies strongly affected soil ecosystems of their nesting islands, but causal correlations between arthropod densities and soil factors were difficult to reveal. One likely reason may be that nesting cormorant islands are very heterogeneous habitats showing large spatial variation in both soil properties as well as fauna densities.
|
|
| 9. |
- Koponen, Hannu T., et al.
(författare)
-
Soil bacterial growth after a freezing/thawing event
- 2016
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 100, s. 229-232
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial growth after freezing/thawing was studied in two soils with a history of annual freezing/thawing events. Soil samples were frozen for 1 week at −3 °C or −18 °C, thawed at +4 °C, and respiration and bacterial growth (estimated using leucine incorporation) were compared with reference soils kept at +4 °C. There were no major differences between soils. A respiration pulse, peaking within 9 h, was found, but after 30–100 h respiration had decreased to that in the reference. Freezing at −18 °C resulted in 2.2–2.5 times higher cumulative respiration than the reference, while at −3 °C 1.6–1.8 times higher respiration was found. Bacterial growth rates immediately after thawing were 43–44% of the reference in the −3 °C and 23–26% in the −18 °C treatment. Growth rates then increased linearly, recovering after 36 h and around 50 h in the −3 °C and −18 °C freezing, respectively. Growth rates then increased further in the −18 °C, but remained lower or similar to the reference in the −3 °C treatment. The microbial response to freezing/thawing thus appeared similar to mild drying/rewetting (type 1 response sensu Meisner et al. (2015)).
|
|
| 10. |
- Meisner, Annelein, et al.
(författare)
-
Partial drying accelerates bacterial growth recovery to rewetting
- 2017
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 112, s. 269-276
-
Tidskriftsartikel (refereegranskat)abstract
- Fluctuations in soil moisture create drying-rewetting events affecting the activity of microorganisms. Microbial responses to drying-rewetting are mostly studied in soils that are air-dried before rewetting. Upon rewetting, two patterns of bacterial growth have been observed. In the Type 1 pattern, bacterial growth rates increase immediately in a linear fashion. In the Type 2 pattern, bacterial growth rates increase exponentially after a lag period. However, soils are often only partially dried. Partial drying (higher remaining moisture content before rewetting) may be considered a less harsh treatment compared with air-drying. We hypothesized that a soil with a Type 2 response upon rewetting air-dried soil would transform into a Type 1 response if dried partially before rewetting. Two soils were dried to a gradient of different moisture content. Respiration and bacterial growth rates were then measured before and during 48 h after rewetting to 50% of water holding capacity (WHC). Initial moisture content determined growth and respiration in a sigmoidal fashion, with lowest activity in air-dried soil and maximum above ca. 30% WHC. Partial drying resulted in shorter lag periods, shorter recovery times and lower maximum bacterial growth rates after rewetting. The respiration after rewetting was lower when soil was partially dried and higher when soils were air-dried. The threshold moisture content where transition from a Type 2 to a Type 1 response occurred was about 14% WHC, while >30% WHC resulted in no rewetting effect. We combine our result with other recent reports to propose a framework of response patterns after drying-rewetting, where the harshness of drying determines the response pattern of bacteria upon rewetting dried soils.
|
|
