The inhibition of fungal cellulolysis by cell-free preparations from ruminococci

Abstract

The degradation of filter paper by the anaerobic fungus Neocallimastix frontalis strain RE1 was reduced by the addition of cell-free supernates from cultures of Ruminococcus albus strain J6 and R. flavefaciens strains 17 and 007. Fungal uptake of, and growth on, glucose was not affected. After gel permeation and anion exchange chromatography, inhibitory activity towards fungal cellulolysis was recovered in a fraction from strain 17 that contained at least five negatively charged polypeptide components, molecular mass 45-68 kDa, on SDS-PAGE.

Antibiosis between Ruminal Bacteria and Ruminal Fungi

“…Stewart et al (52) observed an inhibition in cellulose digestion by N. frontalis RE1 when cell culture supernatants from R. albus or R. flavefaciens fermentations were added; however, growth of the fungus on glucose was not inhibited by addition of the supernatant. The inhibitory activity was destroyed by autoclaving at 121°C for 15 min, and based on gel permeation and anion-exchange chromatography, appeared to consist of several polypeptides.…”

The Rumen Microbial Ecosystem

“…There is as yet no direct evidence that suggests that anaerobic fungi can grow in any portion of the alimentary tract other than the rumen, but it is clear that viable fungi are present in the faeces of ruminants. Specific interactions have been demon-strated in vitro between anaerobic fungi and rumen bacteria which may affect their lignocellulolytic activity in vivo (Bernalier et al, , 1994Stewart et al, 1992) and thus may affect rumen fungal growth. Interactions with methanogens is known to increase the growth of fungi (Williams et ai., 1994), and in initial isolation of fungi from rumen contents it is sometimes difficult to remove methanogens from the culture.…”

Effect of anaerobic fungi on glycoside hydrolase and polysaccharide depolymerase activities, in sacco straw degradation and volatile fatty acid concentrations in the rumen of gnotobiotically reared lambs

“…The recalcitrant lignocellulosic structures that are the most difficult to degrade are generally those that are the most abundantly colonized (Akin, 1987;Bauchop, 1989;Grenet and Barry, 1988). In addition, anaerobic fungi have the necessary array of enzymes to degrade all plant cell wall polymers except lignin (Williams and Orpin, 1987;H6braud and F6vre, 1988 Bernalier et al, 1992Bernalier et al, , 1993Stewart et al, 1992;Roger ef al, 1993). The species composition of the ruminal cellulolytic microflora harboured by the lambs was not determined, but it was probable that the ruminococci were members of this population.…”

“…Any attempt to optimize rumen function, notably experiments designed to improve degradation of the cellwall polymers, cellulose and hemicellulose, will require a fuller understanding of the role and activity of the different hydrolytic microorganisms. There have been numerous studies on the activity of the main fungal and cellulolytic bacterial species in vitro (Fonty et al, 1988a;Orpin and Joblin, 1988;Stewart and Bryant, 1988;Fonty and Joblin, 1991) and their interactions in cellulolysis have been studied in cocultures (Bernalier et al, 1992(Bernalier et al, , 1993Roger et al, 1992Roger et al, , 1993Stewart et al, 1992;Williams et al, 1994 (Mann and Stewart, 1974;Lysons et al, 1976;Hobson et al, 1981;Fonty et al, 1983Fonty et al, , 1988b. Nevertheless, the activity of the 3 main cellulolytic bacterial species, Fibrobacter (Bacteroides) succinogenes, Ruminococcus flavefaciens and R albus, alone or in association, and that of of a fungal flora have been studied in newborn lambs (Fonty et al, 1988c; …”