Effect of short term variation in temperature and water content on the bacterial community in a tropical soil

The community dynamics of environmental bacteria is dependent on micro-climatic factors such as temperature and water potentials. A shift in any one of these factors can have a major impact on the richness and composition of the microbes in the soil. However, microbial responses towards these climate stressors are poorly characterised. Here, we undertook a microcosm study to assess the effect of temperature and water content on the bacterial community structure in a tropical soil over a four week period. The microcosms were incubated at three different temperatures (25 °C, 30 °C, and 35 °C) and maintained under two different water levels (2 and 5 mL). Using a combination of molecular assessment tools and numerical inference, we showed that short-term variation in both temperature and water content induced significant changes to the soil bacterial community composition. The greatest difference in community structure between treatments was observed in the Week 2 microcosms, but in the Week 4 microcosms, the community structure between treatments became more similar. Compared to temperature, water content exerted a greater effect on the bacterial diversity. Firmicutes was the most abundant phylum in all the analysed samples, and its relative abundance increased with elevation in temperature and water content. Out of six functional genes analysed, the nitrogen fixation gene (nifH) and denitrification gene (nosZ) showed significant correlations to the bacterial community structures.