Survival of and plasmid stability in Pseudomonas and Klebsiella spp. introduced into agricultural drainage water

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Abstract
Cell survival and plasmid stability in Pseudomonas fluorescens R2f and Pseudomonas putida CYM 318 containing respectively, plasmid RP4 and pRK2501, and Klebsiella aerogenes NCTC 418 harboring plasmid pBR322 were studied in sterile and nonsterile agricultural drainage water under both aerobic and anaerobic conditions and in the absence and presence of added nutrients. Both Pseudomonas strains survived well in sterile drainage water incubated aerobically, with or without added nutrients. However, Klebsiella aerogenes NCTC 418 (pBR322) only survived in the presence of added nutrients. Pseudomonas fluorescens R2f (RP4) and K. aerogenes NCTC 418 (pBR322) did not survive under anerobic conditions without added nutrients, but showed good survival in the presence of nutrients. Survival of all three strains was negatively affected in nonsterile agricultural drainage water when compared with survival in sterile water. Maintenance of the three plasmids was host, plasmid, and environment dependent. Plasmid pBR322 was not stably maintained in K. aerogenes NCTC 418 under all conditions used in the study, and pRK2501 was readily lost from P. putida CYM 318. Maintenance of RP4 by P. fluorescens R2f was markedly influenced by added nutrients, which caused a loss of the plasmid from cells. The results of the present study demonstrate the influence of nutrients, O2, and native microorganisms on the survival of introduced bacterial strains and plasmid stability in agricultural drainage water.Key words: bacteria, survival, stability, plasmids, water.