Temperature-Driven Adaptation of the Bacterial Community in Peat Measured by Using Thymidine and Leucine Incorporation

Abstract

The temperature-driven adaptation of the bacterial community in peat was studied, by altering temperature to simulate self-heating and a subsequent return to mesophilic conditions. The technique used consisted of extracting the bacterial community from peat using homogenization-centrifugation and measuring the rates of thymidine (TdR) or leucine (Leu) incorporation by the extracted bacterial community at different temperatures. Increasing the peat incubation temperature from 25°C to 35, 45, or 55°C resulted in a selection of bacterial communities whose optimum temperatures for activity correlated to the peat incubation temperatures. Although TdR and Leu incorporations were significantly correlated, the Leu/TdR incorporation ratios were affected by temperature. Higher Leu/TdR incorporation ratios were found at higher temperatures of incubation of the extracted bacterial community. Higher Leu/TdR incorporation ratios were also found for bacteria in peat samples incubated at higher temperatures. The reappearance of the mesophilic community and disappearance of the thermophilic community when the incubation temperature of the peat was shifted down were monitored by measuring TdR incorporation at 55°C (thermophilic activity) and 25°C (mesophilic activity). Shifting the peat incubation temperature from 55 to 25°C resulted in a recovery of the mesophilic activity, with a subsequent disappearance of the thermophilic activity. The availability of substrate for bacterial growth varied over time and among different peat samples. To avoid confounding effects of substrate availability, a temperature adaptation index was calculated. This index consisted of the log 10 ratio of TdR incorporation at 55 and 25°C. The temperature index decreased linearly with time, indicating that no thermophilic activity would be detected by the TdR technique 1 month after the temperature downshift. There were no differences between the slopes of the temperature adaptation indices over time for peat samples incubated at 55°C 3 or 11 days before incubation at 25°C. Thus, different levels of bacterial activity did not affect the temperature-driven adaptation of the bacterial community.Peat is a common substrate used for plant cultivation. After peat is harvested, it is usually collected into stockpiles, which sometimes during the storage period can undergo self-heating. This results not only in substantial losses of material (losses of up to 50% of the substance have been reported [20]) but also in a peat product that may inhibit seed germination and plant growth (23,38).From a microbiological point of view, self-heating and the subsequent cooling period can be considered two phases with extremely different selection pressures, the first selecting for a more thermophilic community and the second selecting for a mesophilic community when the temperature drops. The usual approach to studying such transition phenomena has been to use agar plates incubated at different temperatures, e.g., at around room temperature to indicate the mesophilic community ...

Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders

“…The presence of Ktedonobacterialike taxa in Bare cinders is consistent with results from Ranneklev and Bååth (2001), which indicate that fluctuating thermal regimes can select for and maintain thermophilic or thermotolerant communities simultaneously with mesophilic communities.…”

“…Several previous studies (Ranneklev and Bååth, 2001;Pettersson and Bååth, 2003;Hartley and Hopkins, 2008;Bárcenas-Moreno et al, 2009) have demonstrated that soil microbial communities can adapt to elevated temperature regimes. For example, using growth rate as a variable, Ranneklev and Bååth (2001) have shown that heating peat soil from 25-55 1C resulted in community adaptation with optimal growth at 55 1C in only 3 days.…”

“…For example, using growth rate as a variable, Ranneklev and Bååth (2001) have shown that heating peat soil from 25-55 1C resulted in community adaptation with optimal growth at 55 1C in only 3 days. Heating resulted in rapid growth of thermophiles due to limited substrate competition and additional resources from mesophilic bacterial necromass (Bárcenas-Moreno et al, 2009).…”

Q10 values vary with different kinetic properties of C mineralization

“…As previously reported (Bárcenas-Moreno et al, 2009;Hamdi et al, 2013;Ranneklev and Bååth, 2001), the varying temperature regime (V T ) can promote the optimal growth of most mesophilic microbial groups. In addition, highly diversified microbial pathways increase the exploitation of C resources and the size of the labile C pool (Bracho et al, 2016;Sun et al, 2016).…”

“…Furthermore, the temperature sensitivity of C mineralization not only varies in those kinetic properties, which are partially determined by soil properties , but also changes with environmental conditions, such as constant vs. varying temperature regimes (Conant et al, 2008;Fang et al, 2005;Nakajima et al, 2016;Xia et al, 2009;Zhu and Cheng, 2011), the aeration statuses (Blagodatskaya et al, 2014;Devêvre and Horwáth, 2000;Diakova et al, 2016), the forest stands (Guo et al, 2016;Gutiérrez-Girón et al, 2015;Rey and Jarvis, 2006), and the soil horizons (Laganière et al, 2015;Xu et al, 2014). These constraints, especially the temperature and the aeration status, are fixed as constant in most studies, and a continuously changing vs. constant environmental comparison has rarely been scrutinized (Conant et al, 2008;Hartley et al, 2008;Pettersson and Bååth, 2003;Ranneklev and Bååth, 2001).…”