Antagonistic interaction networks among bacteria from a cold soil environment.

Microbial antagonism in an Arctic soil habitat was demonstrated by assessing the inhibitory interactions between bacterial isolates from the same location. Of 139 isolates obtained from five soil samples, 20 antagonists belonging to the genera, Arthrobacter, Pseudomonas and Flavobacterium were identified. Inter-genus, inter-species and inter-strain antagonism was observed between the interacting members. The extent of antagonism was temperature dependent. In some cases, antagonism was enhanced at 4 °C but suppressed at 18 °C while in some the reverse phenomenon was observed. To interpret antagonism from an ecological perspective, the interacting members were delineated according to their positional roles in a theoretical antagonistic network. When only one antimicrobial producer (P) was present, all the other members permitted grouping into either sensitive (S) or resistant (R). Composite interactive types such as PSR, PS, PR or SR could be designated only when at least two producers were present. Mapping of all possible antagonistic interaction networks based on the individual positional roles of the interactive types illustrates the existence of complex and interconnected networks among microbial communities.