Abstract
The potential of the culturable bacterial community from an Alpine coniferous forest site for the degradation of organic polymers and pollutants at low (5 °C) and moderate (20 °C) temperatures was evaluated. The majority of the 68 strains belonged to the phylum Proteobacteria (77%). Other strains were related to Bacteroidetes (12%), Alphaproteobacteria (4%), Actinobacteria (3%), and Firmicutes (3%). The strains were grouped into 42 different OTUs. The highest bacterial diversity was found within the phylum Bacteroidetes. All strains, except one, could grow at temperatures from 5 to 25 °C. The production of enzyme activities involved in the degradation of organic polymers present in plant litter (carboxymethyl cellulose, microgranular cellulose, xylan, polygalacturonic acid) was almost comparable at 5 °C (68%) and 20 °C (63%). Utilizers of lignin compounds (lignosulfonic acid, lignin alkali) as sole carbon source were found to a higher extent at 20 °C (57%) than at 5 °C (24%), but the relative fractions among positively tested strains utilizing these compounds were almost identical at the two temperatures. Similar results were noted for utilizers of organic pollutants (n-hexadecane, diesel oil, phenol, glyphosate) as sole carbon source. More than two-thirds showed constitutively expressed catechol-1,2-dioxygenase activity both at 5 °C (74%) and 20 °C (66%). Complete phenol (2.5 mmol/L) degradation by strain Paraburkholderia aromaticivorans AR20-38 was demonstrated at 0–30 °C, amounts up to 7.5 mmol/L phenol were fully degraded at 10–30 °C. These results are useful to better understand the effect of changing temperatures on microorganisms involved in litter degradation and nutrient turnover in Alpine forest soils.
Highlights
Climate change is increasing surface temperatures worldwide and is one of the largest challenges facing our planet
All representatives of Betaproteobacteria belonged to the order Burkholderiales, with a predominance of the genera Paraburkholderia and Caballeronia; Xanthomonadales dominated among Gammaproteobacteria
The fraction of Gram-positive bacteria (6%) was very low compared with the fraction of Gram-negative bacteria (94%)
Summary
Climate change is increasing surface temperatures worldwide and is one of the largest challenges facing our planet. Besides a number of physical and chemical alterations, such as increasing soil temperatures, carbon dioxide levels, or nitrogen deposition, climate change will affect the structure, diversity, and abundance of soil microbial communities. Knowledge on the response of soil microorganisms to environmental changes is essential to understand and predict ecosystem processes (Li et al 2014).
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