Fate in water of a recombinantEscherichia coli K-12 strain used in the commercial production of bovine somatotropin

Death of the Escherichia coli K-12 strain W3110 in soil and water

Whether Escherichia coli K-12 strain W3110 can enter the "viable but nonculturable" state was studied with sterile and nonsterile water and soil at various temperatures. In nonsterile river water, the plate counts of added E. coli cells dropped to less than 10 CFU/ml in less than 10 days. Acridine orange direct counts, direct viable counts, most-probable-number estimates, and PCR analyses indicated that the added E. coli cells were disappearing from the water in parallel with the number of CFU. Similar results were obtained with nonsterile soil, although the decline of the added E. coli was slower. In sterile water or soil, the added E. coli persisted for much longer, often without any decline in the plate counts even after 50 days. In sterile river water at 37 degrees C and sterile artificial seawater at 20 and 37 degrees C, the plate counts declined by 3 to 5 orders of magnitude, while the acridine orange direct counts remained unchanged. However, direct viable counts and various resuscitation studies all indicated that the nonculturable cells were nonviable. Thus, in either sterile or nonsterile water and soil, the decline in plate counts of E. coli K-12 strain W3110 is not due to the cells entering the viable but nonculturable state, but is simply due to their death.

Potential for gene transfer from recombinant Escherichia coli K-12 used in bovine somatotropin production to indigenous bacteria in river water

This study examined the transfer of the plasmid pBGH1, an expression vector for bovine somatotropin (BST), from Escherichia coli K-12 strain W3110G [pBGH1] to indigenous microorganisms present in flasks containing Missouri River water. Strain LBB269 is a nalidixic acid-resistant derivative of W3110G which was used as a plasmid-free control strain in these studies. Water samples were inoculated with strains W3110G [pBGH1] and LBB269; after 21 days of incubation the number of viable colony-forming units (CFU) of W3110G [pBGH1] and LBB269 were reduced from an initial level of about 1 x 10(7) CFU per ml to less than 1 CFU per 100 ml. At this time indigenous microbes resistant to both ampicillin and tetracycline (the antibiotic resistance markers on pBGH1) were isolated from 100 ml of water from each of the flasks inoculated with either strain W3110G [pBGH1] or LBB269. Plasmid DNA was isolated from these organisms and examined for sequences containing the gene for BST from pBGH1, using a polymerase chain reaction (PCR) assay. As expected, the day 0 sample from the flask inoculated with E. coli K-12 strain W3110G [pBGH1] gave a positive PCR response and the day 0 sample from the flask inoculated with E. coli K-12 strain LBB269 gave a negative PCR response. All of the day 21 samples containing indigenous microbes isolated from flasks that were inoculated with either W3110G [pBGH1] or LBB269 were negative in the PCR assay, indicating that the target sequence from pBGH1 was not present in any of these indigenous microorganisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Fate in sewage of a recombinant Escherichia coli K-12 strain used in the commercial production of bovine somatotropin

The fate of a derivative of Escherichia coli strain W3110G [pBGH1], a strain used for production of bovine somatotropin, was examined in semi-continuous activated sludge (SCAS) units. A nalidixic acid-resistant derivative of W3110G [pBGH1], strain LBB270 [pBGH1], was used to facilitate tracking. SCAS units (300 ml) containing municipal mixed liquor were operated on a daily cycle of 23 h aeration and 1 h setting followed by decanting of clear supernatant (175 ml) and refilling with fresh primary effluent. SCAS units were inoculated with two concentrations of E. coli LBB270 [pBGH1] and operated for 200 h. Viable levels of E. coli LBB270 [pBGH1] were measured daily in aerated mixed liquor and decanted supernatant. Viable counts in the mixed liquor decreased from 10,000- to 100,000-fold in less than 200 h. Losses of E. coli LBB270 [pBGH1] in decanted supernatants accounted for less than 2-fold of the total losses observed in the SCAS units. The E. coli LBB270 [pBGH1] was not evenly distributed in the mixed liquor, but became preferentially associated with the settleable floc. These results show that E. coli LBB270 [pBGH1] was unable to survive in municipal sludge even when inoculated at concentrations greater than, or comparable to, levels of indigenous microorganisms.

Environmental assessment of recombinant DNA fermentations

This issue of the Journal of Industrial Microbiology contains a compilation of papers presented at the 1992 National Meeting of the Society for Industrial Microbiology in two symposia entitled 'Environmental Assessment of Recombinant DNA Fermentations'. It focuses on three areas of particular interest to industry using Escherichia coli K-12 strains to make recombinant proteins: (i) the current regulatory environment; (ii) plant design; (iii) results from five different companies all of whom are using or planning to use recombinant E. coli in commercial fermentations. The results from all five companies pursuing the questions of environmental fate and the potential for gene transfer in different studies reached the same conclusions. That is, recombinant E. coli K-12 strains and their plasmidless hosts were unable to survive in any environmental microcosm tested. Additionally, there was absolutely no evidence of gene transfer despite the use of highly sensitive techniques to measure such an event. It seems reasonable to conclude that E. coli K-12 strains with recombinant, non-conjugating, poorly mobilizable plasmids do not represent environmental hazards in the event of an accidental release of such microorganisms into the environment.