The unusual cellulose utilization system of the aerobic soil bacterium Cytophaga hutchinsonii

Yongtao Zhu*, Mark J. McBride

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

37 Citations (Scopus)

Abstract

Cellulolytic microorganisms play important roles in global carbon cycling and have evolved diverse strategies to digest cellulose. Some are ‘generous,’ releasing soluble sugars from cellulose extracellularly to feed both themselves and their neighbors. The gliding soil bacterium Cytophaga hutchinsonii exhibits a more ‘selfish’ strategy. It digests crystalline cellulose using cell-associated cellulases and releases little soluble sugar outside of the cell. The mechanism of C. hutchinsonii cellulose utilization is still poorly understood. In this review, we discuss novel aspects of the C. hutchinsonii cellulolytic system. Recently developed genetic manipulation tools allowed the identification of proteins involved in C. hutchinsonii cellulose utilization. These include periplasmic and cell-surface endoglucanases and novel cellulose-binding proteins. The recently discovered type IX secretion system is needed for cellulose utilization and appears to deliver some of the cellulolytic enzymes and other proteins to the cell surface. The requirement for periplasmic endoglucanases for cellulose utilization is unusual and suggests that cello-oligomers must be imported across the outer membrane before being further digested. Cellobiohydrolases or other predicted processive cellulases that play important roles in many other cellulolytic bacteria appear to be absent in C. hutchinsonii. Cells of C. hutchinsonii attach to and glide along cellulose fibers, which may allow them to find sites most amenable to attack. A model of C. hutchinsonii cellulose utilization summarizing recent progress is proposed.

Original languageEnglish
Pages (from-to)7113-7127
Number of pages15
JournalApplied Microbiology and Biotechnology
Volume101
Issue number19
DOIs
Publication statusPublished - 1 Oct 2017
Externally publishedYes

Keywords

  • Cellulase
  • Cellulose digestion
  • Cytophaga hutchinsonii
  • Genetic tools
  • Gliding motility
  • Type IX secretion system

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