The effect of a mixture of four indigenous bacterial genera composed of Bacillus, Pseudomonas, Acinetobacter and Flavobacterium on egg hatchability and larval viability of Clarias gariepinus was investigated. The fertilized eggs were distributed into glass Petri dishes (100 mm diameter) containing 50 ml of water at graded level of mixed indigenous probiotics ranging from 0-108 cells/ml. The incubation time increased from 17 hours at 0 cfu/ml to 22 hours at 108 cfu/ml. The mean hatching rate increased from 8.70% at 0 cfu/ml to 53.85% at 108 cfu/ml. The highest larval survival of 71.43% recorded at 108 cfu/ml where the highest hatching rate was observed, was significantly higher than the larval survival rate observed at the other concentrations. All yolk sac larvae at 0 and 101 cfu/ml died before the end of yolk sac period. These results imply that the incubation time, hatching rate and larval survival of Clarias gariepinus increased with increase in bacterial load of water up to 108 cells/ml, the highest dose employed. Further investigations are needed to establish the optimal and threshold doses

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The culturable bacteria associated with the digestive tract of a freshwater cultured fish, Clarias gariepinus, and their degradative abilities were established. The spread plate method was employed for bacterial isolation. The bacterial isolates were qualitatively screened for extracellular enzyme-producing ability using milk agar, starch agar, egg yolk agar and cellulose agar for protease, amylase, lipase and cellulase activities respectively. A total of 18 bacterial isolates were identified. Bacteria of the genera Bacillus, Staphylococcus, Vibrio, Aeromonas, Pseudomonas, Lactobacillus, Escherichia, Salmonella, Enterobacter, Micrococcus and Flavobacterium were isolated from fish digestive tract at different frequencies with Bacillus predominating. Enzymatic studies indicated that the bacterial isolates possess the ability to degrade proteins, starch, lipids and cellulose. The percentage composition of enzyme-producing bacteria are -protease producing strains (72.2%), lipase producing strains (61.1%), amylase producing strains (55.6%) and cellulose producing strains (38.9%). All the isolates possessed multienzyme activity. An isolate (Bacillus sp. B 1 ) showed activity for protease, amylase, lipase and cellulase enzymes. Therefore, the isolated indigenous multiple enzyme-producing strains can be effectively exploited for use as probiotics while formulating aquafeeds.

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ABSTRACT:The isolation and characterization of hydrocarbon-utilizing bacteria from petroleum oily sludge collected from crude oil processing plant in Rivers State, Nigeria was carried out. Microbiological analysis of the sludge sample showed that the microbial load consisted average of 2.5 x 10 6 cfu/g total heterotrophic bacterial (THB) count, while the hydrocarbon utilizing bacterial (HUB) count was average of 2.0 x 10 3 cfu/g. Phenotypic characteristics and phylogenetic analysis of the 16S rRNA gene sequence of the isolates revealed that they were related to members of the species Klebsiella pneumonia, Klebsiella oxytoca and Alcaligenes faecalis. The 16S rRNA of the isolates showed percentage similarities to the type strains (99% sequence similarities) of the following; Klebsiella pneumonia strain B21 (gi: 922317936), Klebsella pneumonia strain ICB-C183 (gi: 908478837), Klebsella oxytoca strain BCNAI (gi: 846993354), Klebsella oxytoca strain BC4 (gi: 884060138), Alcaligenes faecalis strain IOU PMR (gi: 686028963) and Alcaligenes faecalis strain AQ-I (gi: 816845513). Of the six hydrocarbon utilizing bacteria identified, 4(67%) were Klebsiella species while 2(33%) were identified as Alcaligenes sp of different strains. The result suggest that these isolated organisms from the petroleum sludge can be explored and used to promote environmentally friendly technology clean-up of petroleum hydrocarbon polluted sites in the Niger Delta region of Nigeria.© JASEM https://dx.doi.org/10.4314/jasem.v21i2.17