Improved Recoverability of Microbial Colonies from Marine Sponge Samples J. B. Olson, 1 C. C. Lord, 2 P. J. McCarthy 1 1 Division of Biomedical Marine Research, Harbor Branch Oceanographic Institution, Fort Pierce, FL 34946, USA 2 Florida Medical Entomology Laboratory, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL 32962 USA Received: 24 January 2000; Accepted: 9 June 2000; Online Publication: 28 August 2000 A B S T R A C T The growth of microorganisms from marine sponge samples was studied on various low to high nutrient solid media using media supplements. The supplements utilized were catalase, sodium pyruvate, and a combination of the two. Medium composition was found to influence the growth response on the supplemented media. Microorganisms on low nutrient media responded more favorably to the media additions than on high nutrient media. Thirty-five percent of the supple- mented media demonstrated colony forming unit (CFU) recoveries that were 50% or greater than those of the unamended control plates. Twenty-one percent showed recoveries of more than 100% of the control values, with sodium pyruvate additions providing for the greatest overall increase in recovery, whether alone or in conjunction with catalase. These findings suggest that addition of catalase or sodium pyruvate to solid growth and isolation media may improve recoverability of microorganisms from natural samples. Introduction Analyses of microbial communities have been hindered by our inability to cultivate most of the organisms within a sample. Estimates of bacterial recoverability from environ- mental samples range from 0.01% to 12.5% of the existing community [1, 25, 28]. Some environmental recoverability estimates are derived from comparisons of direct counts of bacteria (using stains such as acridine orange or DAPI) and counts of cultivated colonies (e.g., [6, 12]). Unfortunately, this method of approximating the number of bacteria in a given sample is not effective for examining microbial com- munities associated with a living host. The stains detect nucleic acids and do not differentiate between those of the bacteria and of the host organism [9]. This becomes espe- cially problematic when potentially dealing with large num- bers of intracellular bacteria (within host cells). Numerous methods have been employed in attempts to increase the Correspondence to: J. Olson; Harbor Branch Oceanographic Institution, 5600 US 1 North, Fort Pierce FL 34946, USA; Fax: (561) 461-2221; E-mail: jolson@hboi.edu MICROBIAL ECOLOGY Microb Ecol (2000) 40:139–147 DOI: 10.1007/s002480000058 © 2000 Springer-Verlag New York Inc.