The Fibrobacteres: an Important Phylum of Cellulose-Degrading Bacteria

Abstract

The phylum Fibrobacteres currently comprises one formal genus, Fibrobacter, and two cultured species, Fibrobacter succinogenes and Fibrobacter intestinalis, that are recognised as major bacterial degraders of lignocellulosic material in the herbivore gut. Historically, members of the genus Fibrobacter were thought to only occupy mammalian intestinal tracts. However, recent 16S rRNA gene-targeted molecular approaches have demonstrated that novel centres of variation within the genus Fibrobacter are present in landfill sites and freshwater lakes, and their relative abundance suggests a potential role for fibrobacters in cellulose degradation beyond the herbivore gut. Furthermore, a novel subphylum within the Fibrobacteres has been detected in the gut of wood-feeding termites, and proteomic analyses have confirmed their involvement in cellulose hydrolysis. The genome sequence of F. succinogenes rumen strain S85 has recently suggested that within this group of organisms a "third" way of attacking the most abundant form of organic carbon in the biosphere, cellulose, has evolved. This observation not only has evolutionary significance, but the superior efficiency of anaerobic cellulose hydrolysis by Fibrobacter spp., in comparison to other cellulolytic rumen bacteria that typically utilise membrane-bound enzyme complexes (cellulosomes), may be explained by this novel cellulase system. There are few bacterial phyla with potential functional importance for which there is such a paucity of phenotypic and functional data. In this review, we highlight current knowledge of the Fibrobacteres phylum, its taxonomy, phylogeny, ecology and potential as a source of novel glycosyl hydrolases of biotechnological importance.

Structure, variation, and assembly of the root-associated microbiomes of rice

“…Most of the OTUs enriched between the rhizoplane and endosphere compartments belonged to Alpha-, Beta-, and Deltaproteobacterial classes, Chloroflexi, and Bacteroidetes. Not surprisingly, a subset of the OTUs enriched in the endosphere and rhizoplane belong to Fibrobacteres and Spirochaetes, phyla that are associated with cellulose degradation (24,25).…”

Microdiversity of extracellular enzyme genes among sequenced prokaryotic genomes

“…Commensal or pathogenic strains may have greater access to more labile nutrients than their free-living counterparts, alleviating the necessity for extracellular enzymes. We notably did not detect the ability to use phosphate esters or chitin within Fibrobacteres, a gut symbiont (Ransom-Jones et al, 2012), or Chlamydiae, an obligate intracellular pathogen (Horn, 2008). Recently, Luo et al (2011) found that environmental isolates of E. coli shared a set of genes important for resource acquisition that were absent from enteric isolates.…”

Multidisciplinary approach to assess the water self-depuration characteristics of Suquía River (Córdoba, Argentina)

“…Diverse cellulolytic species have the capacity to produce celulolase enzymes in aerobic and anaerobic conditions (Kumar et al 2008). It was informed that cellulose global degradation occurs in aerobic conditions in 90% and in anaerobic conditions in 10% (Wei et al 2009;Ransom-Jones et al 2012). The fact that in this work cellulolytic microorganisms were detected in both aerobic and anaerobic environments indicates that the degradation of cellulose occurs in both conditions.…”