Chitin degradation and utilization by virulent Aeromonas hydrophila strain ML10-51K
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ORIGINAL PAPER
Chitin degradation and utilization by virulent Aeromonas hydrophila strain ML10‑51K Dunhua Zhang1 · De‑Hai Xu1 · Junqiang Qiu2 · Cody R. Rasmussen‑Ivey3 · Mark R. Liles3 · Benjamin H. Beck1
Received: 25 September 2016 / Revised: 28 November 2016 / Accepted: 7 December 2016 © Springer-Verlag Berlin Heidelberg (outside the USA) 2016
Abstract Virulent Aeromonas hydrophila (vAh) is one of the most important bacterial pathogens that causes persistent outbreaks of motile Aeromonas septicemia in warmwater fishes. The survivability of this pathogen in aquatic environments is of great concern. The aim of this study was to determine the capability of the vAh strain ML1051K to degrade and utilize chitin. Genome-wide analysis revealed that ML10-51K encodes a suite of proteins for chitin metabolism. Assays in vitro showed that four chitinases, one chitobiase and one chitin-binding protein were secreted extracellularly and participated in chitin degradation. ML10-51K was shown to be able to use not only N-acetylglucosamine and colloidal chitin but also chitin flakes as sole carbon sources for growth. This study indicates that ML10-51K is a highly chitinolytic bacterium and suggests that the capability of effective chitin utilization could enable the bacterium to attain high densities when abundant chitin is available in aquatic niches.
Communicated by Erko Stackebrandt. Electronic supplementary material The online version of this article (doi:10.1007/s00203-016-1326-1) contains supplementary material, which is available to authorized users. * Dunhua Zhang [email protected] 1
Aquatic Animal Health Research Unit, USDA-ARS, 990 Wire Road, Auburn, AL 36832, USA
2
College of Fisheries and Life Sciences, Shanghai Ocean University, Pudong New District, Shanghai 201306, China
3
Department of Biological Sciences, Auburn University, Auburn, AL, USA
Keywords Virulent Aeromonas hydrophila · Chitinase · Chitinolytic enzymes · Chitin degradation · Chitin utilization
Introduction Aeromonas hydrophila, a Gram-negative bacterium, is the causal agent of motile Aeromonas septicemia (MAS) in catfish and other warm-water fishes (Plumb and Hanson 2011). A severe outbreak of MAS in the Southeastern United States was reported in 2009 (Hemstreet 2010); the disease has since resulted in loss of millions of pounds of market-size catfish annually (Bebak et al. 2015; Hossain et al. 2014). Emergence of a new pathotype of virulent A. hydrophila (vAh) was associated with the outbreaks (Griffin et al. 2013; Hossain et al. 2014) but certain aquaculture practices also had an impact on severity of disease severity (Bebak et al. 2015). Earlier studies found that A. hydrophila was more abundant in waters with a high organic load than in relatively unpolluted water (Jeney and Jeney 1995) and MAS outbreaks caused by vAh in crucian carp in China occurred primarily in fish ponds with high organic loads (Nielsen et al. 2001). Since chitin is the major component of organic matter in aquatic ecosystems (Beier and Bertilsson 2011), u
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