Agar plate counts and microbial types are reported for brown shrimp reared in 2-acre natural marshland and in 0.5-acre artificial ponds during June to October 1970. Bacterial counts of pond-reared shrimp ranged from 5 X 104 to 5.5 X 106 per g. At final harvest in October, bacterial counts ranged from 2 x 105 to 5.5 x 108 per g. In marsh ponds, bacterial counts of shrimp and pond water were lowest in August when both water temperature and salinity were high. Coryneform bacteria and to a lesser extent Vibrio were the predominant isolates from fresh pond shrimp. Shrimp stored at 3 to 5 C for 7 days were acceptable as judged by appearance and odor. Between 7 and 14 days of refrigerated storage, bacterial counts increased sharply and about 50% of the samples became unacceptable. Refrigerated storage of pond shrimp caused increases in coryneform bacteria and micrococci and decreases in Vibrio, Flavobacterium, Moraxella, and Bacillus species. Pseudomonas species were not significant in fresh or stored pond shrimp. The microbial flora of pond water usually was dominated by coryneform bacteria, Flavobacterium, Moraxella, and Bacillus species.

Gram-positive, catalase-positive, nonsporeforming, pleomorphic rods isolated from pond-reared shrimp and pond water were compared with type cultures of the Corynebacteriaceae. Classification of the type cultures based on 66 cell and colony characters proved comparable to one based on 163 morphological, biochemical, and physiological characters. This similarity was not observed with pond isolates. With the aid of numerical analysis, pond isolates could be placed into six major groups based on certain biochemical and physiological tests. Coryneform bacteria isolated from shrimp and water exhibited little similarity to the type cultures. The pond isolates probably are members of the Corynebacteriaceae not previously studied in detail. Coryneform bacteria are ubiquitous in the have been isolated from various foods. Splittsnatural environment. Species of Corynebactoesser et al. (5) showed that coryneform bacterium, Arthrobacter, and Microbacterium teria made up a significant part of the mi-'Published with the approval of the Texas Agricultural crobial flora of frozen vegetables. In previous Experiment Station, College Station, Tex. 77843. studies, Vanderzant et al. (6, 7) reported that TABLE 1. Type cultures used for computer analysis Family Genus Species Source Corynebacteriaceae Corynebacterium C. aquaticum ATCC 14665 C. bovis ATCC 7715 C. equi ATCC 6939 C. lilium ATCC C. michiganense ATCC 492 C. pseudodiphtheriticum ATCC C. pseudotuberculosis ATCC 809 C. pyogenes ATCC C. renale ATCC C. rubrum ATCC C. tritici ATCC C. hoffmanni NCTC 231 Arthrobacter A. atrocyaneus ATCC A. flavescens ATCC A. globiformis ATCC 8010 A. tumescens ATCC 6947 Microbacterium M. flavum ATCC M. lacticum ATCC 8181 Propionibacteriaceae Propionibacterium P. arabinosum ATCC 4965 P. rubrum ATCC 4871 Brevibacteriaceae Brevibacterium B. divaricatum ATCC B. linens ATCC 9172