The objective was to characterize sediment Streptomyces from the Laguna Madre, a hypersaline estuary. We hypothesize that different environmental factors (i.e., other microorganisms, salt concentration) will result in spatial differences in Streptomyces communities. Streptomyces are of interest because of their ability to produce a variety of secondary metabolites, such as antibiotics and extracellular enzymes. Sediment samples were collected from 3 sites in the Laguna Madre; two sites were proximal to each other whereas the third site was distal to the others. Triplicate samples were collected at each site, diluted and spread onto Marine 2216 Agar, Oatmeal agar (OA), and Starch Casein agar (SCA). MA and OA plates were used to estimate the overall bacterial density. SCA was used to estimate the density of Streptomyces at each site and for Streptomyces isolation. Eleven Streptomyces isolates were characterized biochemically using API20E® strips. Inhibitory assays were performed on the isolates to determine if there was evidence for increased competition between isolates found in the same location. Results suggest that salt concentration at a specific site had an impact on the density and niche for the microorganisms present; microbial density was similar amongst the close sites vs. the isolated site. Biochemical tests indicated that organisms isolated from all sites had similar enzymatic capabilities, including positive tests for citrate utilization, gelatinase, and nitrite utilization. This suggests Streptomyces in Laguna Madre sediments occupy specialized niches. Current work includes further isolations and characterizations of Streptomyces, and BIOLOG® testing to determine carbon utilization among isolated microorganisms.
