POPULATION-STRUCTURE AND PHYSIOLOGICAL-CHANGES WITHIN A HOT-SPRING MICROBIAL MAT COMMUNITY FOLLOWING DISTURBANCE

The influence of disturbance on a hot spring cyanobacterial mat commun ity was investigated by physically removing the top 3.0 mm, which incl uded the entire cyanobacterial layer, Changes in 16S rRNA-defined popu lations were monitored by denaturing gradient gel electrophoresis anal ysis of PCR-amplified 16S rRNA gene segments. Some previously absent c yanobacterial populations colonized the disturbed areas, while some po pulations which were present before the disturbance remained absent fo r up to 40 days, Changes in physiological activity were measured by ox ygen microelectrode analyses and by (CO2)-C-14 incorporation into cyan obacterial molecular components, These investigations indicated substa ntial differences between the disturbed and undisturbed mats, includin g an unexplained light-induced oxygen consumption in the freshly expos ed mat, increased carbon partitioning by phototrophs into growth-relat ed macromolecules, bimodal vertical photosynthesis profiles, and delay ed recovery of respiration relative to photosynthesis.