Bacterial chitin degradation—mechanisms and ecophysiological strategies

Sara Beier,Stefan Bertilsson

doi:10.3389/fmicb.2013.00149

Abstract

Chitin is one the most abundant polymers in nature and interacts with both carbon and nitrogen cycles. Processes controlling chitin degradation are summarized in reviews published some 20 years ago, but the recent use of culture-independent molecular methods has led to a revised understanding of the ecology and biochemistry of this process and the organisms involved. This review summarizes different mechanisms and the principal steps involved in chitin degradation at a molecular level while also discussing the coupling of community composition to measured chitin hydrolysis activities and substrate uptake. Ecological consequences are then highlighted and discussed with a focus on the cross feeding associated with the different habitats that arise because of the need for extracellular hydrolysis of the chitin polymer prior to metabolic use. Principal environmental drivers of chitin degradation are identified which are likely to influence both community composition of chitin degrading bacteria and measured chitin hydrolysis activities.

Highlights

The occurrence of chitin is widespread in nature and chitin serves as a structural element in many organisms, e.g., fungi, crustaceans, insects or algae (Gooday, 1990a,b)
Chitin hydrolysis rates have been shown to correlate with bacterial abundance (Kielak et al, 2013), but depending on temperature, pH, or the successional stage of the degradation process, fungi may be quantitatively important agents of chitin degradation (Gooday, 1990a; Hallmann et al, 1999; Manucharova et al, 2011)
In aquatic systems, plating and in situ colonization experiments convincingly demonstrates that bacteria are the main mediators of chitin degradation (Aumen, 1980; Gooday, 1990a)

Summary

Introduction

The occurrence of chitin is widespread in nature and chitin serves as a structural element in many organisms, e.g., fungi, crustaceans, insects or algae (Gooday, 1990a,b). In aquatic systems, plating and in situ colonization experiments convincingly demonstrates that bacteria are the main mediators of chitin degradation (Aumen, 1980; Gooday, 1990a). A further source of chitin modifying enzymes in aquatic systems are enzymes released during molting of planktonic crustaceans (Vrba and Machacek, 1994). It is not yet clear whether the enzymes released by diatoms and molting zooplankton react with particulate chitin to any significant extent or if their hydrolytic activity is limited to dissolved chitin oligomers

Methods

Findings

Conclusion