Abstract
We developed a simple method for absorbance spectrophotometry to identify photosynthetic pigments of microbial mats using a portable spectrophotometer in the field. This method was very efficient for the identification of mat-forming phototrophs and estimations of their mixing ratios in the field. It was also applied to describe the structure of hot spring microbial mats developed at the Nakabusa Hot Spring, Nagano Prefecture. The microbial mats consisted of cyanobacteria and Chloroflexus, and their distribution depended on the water temperature. The ratio of these two bacteria determined by absorbance spectra was constant at temperatures ranging from 45 to 60°C, and the spectral mixing ratios of Chloroflexus were about 40%. That ratio increased with temperatures in the range of 60 to 70°C; above 70°C, only Chloroflexus was observed. The spectrophotometry also found a pink bacterial mat which had distinctive absorption peaks at 801 and 878 nm. These peaks strongly suggested that the organism was a novel phototrophic bacterium of a new taxon.
