In vitro stimulation ofBacteroides fragilis growth byEscherichia coli

Abstract

The interaction between Bacteroides fragilis and Escherichia coli was investigated by following their growth kinetics in an in vitro mixed culture system. In Bacto-peptone or in a semisynthetic medium (SSM-M) Bacteroides fragilis could initiate growth only when a small number of viable Escherichia coli initially coexisted for a short period of time. Both Bacto-peptone and SSM-M previously spent by Escherichia coli also allowed Bacteroides fragilis growth to occur but the supplementation of heat killed Escherichia coli cells or viable cell homogenates to fresh media failed to stimulate Bacteroides fragilis growth. The in vitro stimulation of Bacteroides fragilis growth by Escherichia coli observed in this study may be best explained by the combination of (a) removal of oxygen and other toxic substances and (b) de novo production of Bacteroides fragilis growth stimulating factor(s) by coexistent Escherichia coli.

Characterizing mixed microbial population dynamics using time-series analysis

“…In both cases, the smooth functions have a parabolic shape where the covariate species appears to have a positive effect on the response species up to a point where the relationship turns negative (Figures 3a and h). One positive feedback effect of E. coli might have on B. uniformis growth is that of removing residual oxygen from the ambient growth medium (Hagen et al, 1982). At low E. coli abundances this might be beneficial to the strictly anaerobic Bacteroides species, but at a certain level of E. coli abundance the relationship may shift to one of direct competition, outweighing the benefits of oxygen removal and thus having a negative effect on B. uniformis growth.…”

“…In general ecological science one often encounters terms such as within and between species competition, cooperation and density dependence (Turchin, 1995;Stenseth et al, 1998;Ciannelli et al, 2005;Moe et al, 2005). Such concepts are much less frequently explored in the context of microbes (Hagen et al, 1982;Bradshaw et al, 1994;Rainey and Rainey, 2003;You et al, 2004;Balagadde et al, 2005). This is partly due to a historical division between the fields of microbiology and general ecology, but the difficulty of quantitative population data collection from complex microbial systems has also been a major factor contributing to the paucity of information on population dynamics in microcosm.…”

Associations among Health Perceptions and Health Status within Three Age Groups

“…Such growth rates can be frequency dependent due to interactions in the population other than direct competition [63]. Mechanistically, the positive effect of E. coli at low frequency might result from the removal of residual oxygen from the growth medium [67], given that B. uniformis is strictly anaerobic. Linear frequency-dependent growth rates have also been reported in a study of microbial random phase variation, which influences bacterial survival in changing environments [65].…”

Pathogenic synergy between Escherichia coli and Bacteroides fragilis: studies in an experimental mouse model

“…Some authors have reported inhibition of phagocytosis of facultative aerobes in the presence of anaerobes (Ingham et al, 1977;Namavar et al, 1983). Other mechanisms such as growth stimulation of B. fragilis by E. coli as suggested by Hagen et al (1982) may also be involved. The fate of the bacteria during the first 24 h of the experiments has been shown to be crucial for the outcome of infection (Miles et al 1957;Gorrill, 1965).…”