Ecological distribution and biodegradational activities of oil-degrading marine bacteria in the Arabian Gulf water at Kuwait

The distribution of oil-degrading bacteria in the Arabian Gulf water at Kuw ait during the year January-December 1995 was studied. This group of microo rganisms ranged from 0.3 - 15.2 x 10(3) CFU/l in Shuwaikh Station (a commer cial harbour) and 0.1 - 5.8 x 103 CFU/l in Salmiya (a relatively unpolluted control). Their percentages among total heterotrophic bacteria were in the range of 0.2 - 22.8% in Shuwaikh water and 0.1 - 8.8% in Salmiya water. Th e ratios of CFU/l of oil-degrading bacteria obtained from Shuwaikh to that obtained from Salmiya are in the range of 1.5 - 57.0. Autumn and winter were suitable seasons for obtaining high proportions of o il-degrading bacteria, while spring and summer were suitable for the develo pment of large counts of total viable heterotrophic bacteria. The total num ber of viable fungi was greater during spring and autumn. Out of 180 bacterial cultures able to grow in the presence of crude oil, 28 cultures showed good growth. They were Pseudomonas spp. (32.1%), Arthrobac ter spp. (23.1%), Corynebacterium spp. (17.8%), Acinetobacter spp. (10.7%), and Flavobacterium spp. (7.1%). Six of the 28 species were selected and in oculated singly and as mixtures into natural sea water. Arthrobacter sp. A( 1) and Pseudomonas sp. P(6) degraded 64% and 60% of the saturates fraction respectively, which were 15.5% and 11.5% above those degraded in presence a nd in absence of the mixed inoculum of the six species. On the other hand P seudomonas sp. P(8) and Arthrobacter sp. A(2) degraded 30% and 29% of the a romatic fractions, which was 10-12% more than the amounts degraded in the p resence and absence of the mixed inoculum.