BACTERIAL DENSITY AND SURVEY OF CULTIVABLE HETEROTROPHS IN THE SURFACE-WATER OF A FRESH-WATER MARSH HABITAT OF ANOPHELES-QUADRIMACULATUS LARVAE (DIPTERA, CULICIDAE)

We examined surface water samples collected in September and October 1 994 from a freshwater marsh habitat containing larval Anopheles quadri maculatus mosquitoes. Bacterial densities in direct microscopic counts ranged from 9.7 x 10(5) to 1.3 x 10(7) cells/ml. Densities of cultiva ble bacteria on trypticase soy agar medium ranged from 1.0 to 1.5 x 10 (5) cells/ml. The majority of 888 isolates were gram-positive rods (41 %) followed by gram-negative rods (28%). Analysis of the cellular fatt y acid profiles of 824 isolates using gas chromatography and Microbial Identification Systems TSBA (Rev. 3.60) library software grouped the bacteria into Bacillus spp. (35%), other gram-positive bacteria (16%), pseudomonads (15%), other gram-negative bacteria including mainly Ent erobacteriaceae and Vibrionaceae (21%), and profiles not recognized (1 3%). Among 33 genera within these groups, the most common were Bacillu s, Pseudomonas, Aeromonas, and Arthrobacter.