Abstract

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Cultures of algal species are often needed for research purposes. These cultures are frequently accompanied by bacteria that are picked up from the environment together with the algal cells, thus the practice of purifying algal cultures using antibiotics. Water sample from fish pond having algal bloom was inoculated into BG-II medium supplemented with 62.5 ug.mF Chloramphenicol and 100 ug.ml-1 Nystatin. The total heterotrophic bacterial count before the addition of the antibiotics was 3.8xl04cfu.ml1. The bacterial population decreased to an average count of 3.5xl02 cfu.ml1, after a period of 24 hours. This population was made up of three distinct colonies. Colonial morphology and preliminary tests based on physicochemical characteristics gave a probable identification of the isolates as Bacillus, Proteus, and Pseudomonas. The Bacillus showed resistance to Chloramphenicol and Flucloxacillin; Proteus showed resistance to Chloramphenicol, Flucloxacillin, Lincomycin, Erythromycin, Ampicilin, Ampiclox, and Septrin; Pseudomonas showed resistance to all antibiotics used in the investigation with exception to Ciprofloxacin, Streptomycin, and Rifampin, which were effective on the three isolates. The results indicate that certain bacteria that are present in algal cultures can become resistant to several antibiotics as a result of purification of algal cultures using antibiotics at sub lethal dose. It is suggested that screening for effective antibiotic(s) and determination of their minimum inhibitory concentration or minimum lethal concentration, as the case may be, against identified bacteria contaminants be part of the procedure for setting up pure cultures of algae.

Keywords: Antibiotics, Bacillus, Proteus, Pseudomonas, Purifying algal cultures, Resistance to Chloramphenicol,