Competition among three predominant ruminal cellulolytic bacteria in the absence or presence of non-cellulolytic bacteria

Abstract

Competition among three species of ruminal cellulolytic bacteria -Fibrobacter succinogenes S85, Ruminococcus flavefaciens FD-1 and Ruminococcus albus 7 -was studied in the presence or absence of the non-cellulolytic ruminal bacteria Selenomonas ruminantium or Streptococcus bovis. Co-cultures were grown under either batch or continuous conditions and populations were estimated using species-specific oligonucleotide probes to 16S rRNA. The three cellulolytic species co-existed in cellobiose batch co-culture, but inclusion of either Sel. ruminantium or Str. bovis yielded nearly a monoculture of the noncellulolytic competitor. In cellobiose chemostats, R. albus completely dominated the triculture, but R. flavefaciens became predominant over F. succinogenes and R. albus when Sel. ruminantium was co-inoculated into the chemostats. Similar effects on competition were observed in the presence of Str. bovis at a lower (0021 h N1 ), but not at a higher (0045 h N1 ) dilution rate. In cellulose batch co-cultures, R. albus was more abundant than both F. succinogenes and R. flavefaciens, regardless of the presence of the noncellulolytic species. Co-existence among the three cellulolytic species was observed in almost all cellulose chemostats, but Sel. ruminantium altered the relative proportions of the cellulolytic species. R. albus and R. flavefaciens were found to produce inhibitors that suppressed growth of R. flavefaciens and F. succinogenes, respectively. These data indicate that interactions among cellulolytic bacteria, while complex, can be modified further by non-cellulolytic species.

Adhesion to cellulose of the Gram-positive bacterium Ruminococcus albus involves type IV pili The EMBL accession number for the sequence reported in this paper is AJ416469.

“…R. albus was shown to be far more abundant than either R. flavefaciens and F. succinogenes in the bovine rumen whatever diet the animals were fed (Weimer et al, 1999). In vitro studies confirmed that R. albus outcompeted the two other species and became predominant in cultures where the three species were grown in the presence of cellulose as a growth substrate, alone or associated with non-cellulolytic species (Chen & Weimer, 2001). These studies tend to show that R. albus, R. flavefaciens and F. succinogenes do not act synergistically, but rather compete for their substrate, and that R. albus displays several ecological advantages that allow it to compete successfully.…”

Microbial Cellulose Utilization: Fundamentals and Biotechnology

“…While cellulolytic species may compete directly for cellulose (104,192,193,499,616), both cellulolytic and noncellulolytic species can compete for cellodextrin products of cellulose hydrolysis, in cross-feeding of nutrients, and in production of inhibitory compounds. A number of examples of such interactions have been demonstrated in defined mixed cultures (Table 2).…”

Plant Lectin-Like Bacteriocin from a Rhizosphere-Colonizing Pseudomonas Isolate

“…However, we detected two homologues of inh1 in unfinished genomic sequences of R. albus strain 8. inh1 and its two homologues are predicted to encode very similar proteins exhibiting more than 70% sequence identity and comprising a single N-terminal MMBL domain fused to a C-terminal region having an unknown function. Bacteriocins produced by ruminococcal bacteria are said to be part of the survival strategy of ruminal bacteria conferring competitive fitness in the ruminal environment (9). Inh1 and most other MMBL domain proteins of bacterial origin carry a potential N-terminal signal sequence that may direct these proteins to the extracellular environment.…”