Physiology of purple sulfur bacteria forming macroscopic aggregates in Great Sippewissett Salt Marsh, Massachusetts

Abstract

Purple bactenal aggregates found in tidal pools of Great Sippewissett Salt Marsh (Falmouth, Cape Cod, MA) were mvestlgated m order to eluCidate the ecological significance of cell aggregation. Purple sulfur bactena were the dommant microorganisms m the aggregates which also con tamed diatoms and a high number of small rod-shaped bactena. Urea m concentrations of ~ 1 M caused dlsmtegratlOn of the aggregates while proteolytic enzymes, surfactants or chaotropic agents did not exhibit this effect. This suggests that polysaccharides in the embedding slime matrix stabihze the aggregate structure In addition cell surface hydrophoblclty is involved in aggregate formation. The concentration of dissolved oxygen decreased rapidly below the surface of aggregates while sulfide was not detected. The apparent respiration rate m the aggregates was high when the purple sulfur bactena contamed intracellular sulfur globules. In the presence of DCMU, respiratIOn remained hght-mhibited. Light inhibition disappeared in the presence of KCN. These results demonstrated that respiration m the aggregates IS due mamly to purple sulfur bactena The concentration of bactenochlorophyll (Bch\) a in the aggregates (0.205 mg Bchla cm -3) was much higher than m the pool sedlments but comparable to concentrations in microbial mats of adjacent sand fiats. Purple aggregates may therefore onginate m the microbial mats rather than in the pools themselves Rapid sedimentation and high resplfatlOn rates of Chromatiaceae in the aggregates would prevent the mhibitlon of Bchl syntheSIS If aggregates were hfted off the sediment and up mto the OXIC pool water by tidal currents.

Photosynthetic activity and population dynamics of Amoebobacter purpureus in a meromictic saline lake

“…The reduced photosynthetic activity of purple sulfur bacteria during August did not account for the amount of sulfide oxidized in the chemocline. Unlike purple sulfur bacteria in other environments [20], respiratory oxidation of sulfide by A. purpureus cells seems to be insignificant in Mahoney Lake. This compares well with the very low respiration rates determined in pure cultures of A. purpureus [21].…”

Unexpectedly high bacteriochlorophyll a concentrations in neotropical tank bromeliads

“…A and A). Considering the ecology of APB, this last observation is consistent with the ability of these bacteria to form aggregates (Seitz et al ., ) and their clear preference for a particle‐attached lifestyle (Waidner and Kirchman, ; Lami et al ., ; Cottrell et al ., ). Integrated over ecosystem scales, both these results have at least two additional explanations.…”

Unexpected diversity in populations of the many‐celled magnetotactic prokaryote

“…White filaments, presumably sulfur extruded by sulfide‐oxidizing bacteria, were visible near the water edge on some dates. Purple ‘berries’ containing photosynthetic purple sulfur bacteria (Seitz et al ., 1993) were abundant on the sediment surface, especially during mid‐summer sampling. Historical air temperature data for Otis Air Force Base, approximately 10 miles away from the collection site, was obtained from http://www.wunderground.com.…”