Artificial cold-adapted microbial mats cultured from Antarctic lake samples. 1. Formation and structure

Artificial microbial mats were cultured at 4 to 7 degreesC in benthic gradient chambers using inocula of Antarctic lake mats (Lake Fryxell, Dry Valleys). Their formation and structure were studied based on both HPLC pigment quantification and microsensor measurements of oxygen profiles. Accretion rates (2 to 5 mm within the year) were consistent with previous estimations for artificial mats cultured at 17 to 25 degreesC, suggesting that the microbial community was cold-adapted. Mats were vertically structured comprising an upper green layer dominated by cyanobacteria and an underlying pink layer including purple non-sulphur phototrophic bacteria. Pigment contents indicated that both groups of cyanobacteria (Oscillatoriacae and possibly Nostoc sp.) adopted different patterns of vertical distributions within the mats. Heterogeneity of oxygen vertical distributions was determined, and net primary productivity rates were in the range of those previously reported for natural Antarctic microbial mats. Collective considerations of pigment contents and primary productivity strongly suggest that artificial mats presented some characteristics of natural polar mats, although some differences were established.