ISSN:
0006-3592
Keywords:
biofilm formation
;
Escherichia coli
;
C/N ratio
;
plasmid retention
;
extracellular polysaccharide
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Biofilm formation and plasmid segregational instability in biofilm cultures of Escherichia coli DH5α (pMJR1750) were investigated under different medium-carbon-to-nitrogen (C/N) ratios. At C/N ratios of 0.07 and 1, net accumulation of both biofilm plasmid-bearing and plasmid-free cells continued through the entire experiment without attaining any apparent steady state. At C/N ratios of 5 and 10, net biofilm cell accumulation for the two populations reached apparent steady states after 84 and 72 h, respectively. At C/N ratios of 0.07 and 1, polysaccharide production increased slowly and reached about 2g alginate equivalent/cm2 by the end of both experiments. At a C/N ratio of 5, polysaccharide increase significantly after 84 h, reaching about 7μg alginate equivalent/cm2 prior to termination. At a C/N ratio of 10, polysaccharide increased significantly after 72 h and reached 21 μg alginate equivalent/cm2 at 108 h. At C/N ratios of 0.07 and 1, protein production reached 6.5 and 4 μg/cm2, respectively. At C/N ratios of 5 and 10, protein production increased slightly for the first 84 h and reached a maximum at 108 h, at 3 and 2 μg/cm2, respectively, then decreased over the last 12 h of the experiment. Ratios of polysaccharide to protein increased with increasing C/N ratios. At C/N ratios of 0.07 and 1, the ratios between extracellular polysaccharide (EP) and protein were no more than 205 μg polysaccharide/μg protein, whereas those at C/N ratios of 5 and 10 increased to about 7 and 12 μg polysaccharide/μg protein, respectively.Probabilities of plasmid loss in the biofilm cultures increased with increasing C/N ratios. At C/N ratios of 0.07, 1, and 5, the probabilities of plasmid loss were 0.0013 ± 0.011, 0.020 ± 0.006 and 0.122 ± 0.021, respectively. At a C/N ratio of 10, the probability of plasmid loss was significantly higher, reaching 0.38 ± 0.125. The increase of probability of plasmid loss at higher C/N ratios results from competition between cell replication and extracellular polysaccharide production. © 1994 John Wiley & Sons, Inc.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bit.260440310
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