Journal of Microbiology

Research Support, Non-U.S. Gov't

Evidence of Indigenous NAH Plasmid of Naphthalene Degrading Pseudomonas putida PpG7 Strain Implicated in Limonin Degradation: Moushumi Ghosh , Abhijit Ganguli , Meenakshi Mallik; J. Microbiol. 2006;44(5):473-479.; DOI: https://doi.org/2451 [pii]

Abstract: A well characterized naphthalene-degrading strain, Pseudomonas putida PpG7 was observed to utilize limonin, a highly-oxygenated triterpenoid compound as a sole source of carbon and energy. Limonin concentrations evidenced a 64% reduction over 48 h of growth in batch cultures. Attempts were made to acquire a plasmid-less derivative via various methods (viz. Ethidium Bromide, SDS, elevated temperature & mitomycin C), among which the method involving mitomycin C (20 μg/ml) proved successful. Concomitant with the loss of plasmid in P. putida PpG7 strain, the cured derivative was identified as a lim- phenotype. The lim+ phenotype could be conjugally transferred to the cured derivative. Based on the results of curing with mitomycin C, conjugation studies and presence of ndo gene encoding naphthalene 1,2 dioxygenase, it was demonstrated that genes for the limonin utilization were encoded on an 83 kb indigenous transmissible Inc. P9 NAH plasmid in Pseudomonas putida PpG7 strain.

Journal Article

Plasmid Profiling and Curing of Lactobacillus Strains Isolated from the Gastrointestinal Tract of Chicken: Sieo Chin Chin , Norhani Abdullah , Tan Wen Siang , Ho Yin Wan; J. Microbiol. 2005;43(3):251-256.; DOI: https://doi.org/2217 [pii]

Abstract: In this study, we assessed the susceptibility of 12 Lactobacillus strains, all of which had been isolated from the gastrointestinal tracts of chicken, to three antibiotics (chloramphenicol, erythromycin and tetracycline) used commonly as selective markers in transformation studies of lactic acid bacteria. Among these strains, 17%, 58%, and 25% were found to exhibit a high degree of resistance to 200 mg/ml of tetracycline, erythromycin, and chloramphenicol, respectively. Seven of the 12 Lactobacillus strains exhibiting resistance to at least 50 mg/ml of chloramphenicol or erythromycin, and five strains exhibiting resistance to at least 50 mg/ml of tetracycline, were subsequently subjected to plasmid curing with chemical curing agents, such as novobiocin, acriflavin, SDS, and ethidium bromide. In no cases did the antibiotic resistance of these strains prove to be curable, with the exception of the erythromycin resistance exhibited by five Lactobacillus strains (L. acidophilus I16 and I26, L. fermentum I24 and C17, and L. brevis C10). Analysis of the plasmid profiles of these five cured derivatives revealed that all of the derivatives, except for L. acidophilus I16, possessed profiles similar to those of wild-type strains. The curing of L. acidophilus I16 was accompanied by the loss of 4.4 kb, 6.1 kb, and 11.5 kb plasmids.

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