Diversity of Both the Cultivable Protease-Producing Bacteria and Bacterial Extracellular Proteases in the Coastal Sediments of King George Island, Antarctica

Ming-Yang Zhou,Xiu-Lan Chen,Qi-Long Qin,Dan Li,Bo Chen,Yu-Zhong Zhang,Xi-Ying Zhang,Bai-Cheng Zhou,Dian-Li Zhao,Guang-Long Wang,Christina A Kellogg

doi:10.1371/journal.pone.0079668

Abstract

Protease-producing bacteria play a vital role in degrading sedimentary organic nitrogen. However, the diversity of these bacteria and their extracellular proteases in most regions remain unknown. In this paper, the diversity of the cultivable protease-producing bacteria and of bacterial extracellular proteases in the sediments of Maxwell Bay, King George Island, Antarctica was investigated. The cultivable protease-producing bacteria reached 105 cells/g in all 8 sediment samples. The cultivated protease-producing bacteria were mainly affiliated with the phyla Actinobacteria, Firmicutes, Bacteroidetes, and Proteobacteria, and the predominant genera were Bacillus (22.9%), Flavobacterium (21.0%) and Lacinutrix (16.2%). Among these strains, Pseudoalteromonas and Flavobacteria showed relatively high protease production. Inhibitor analysis showed that nearly all the extracellular proteases from the bacteria were serine proteases or metalloproteases. These results begin to address the diversity of protease-producing bacteria and bacterial extracellular proteases in the sediments of the Antarctic Sea.

Highlights

There is abundant particulate organic material in the sea floor
The content of organic carbon (OrgC) and organic nitrogen (OrgN) in the sediments was in the range of 0.32-3.59% (OrgC) and 0.49-1.07% (OrgN); the highest values were obtained from stations SS14 and SS15, and the lowest values were obtained from station SS11 (Table 1)
We investigated the protease-producing bacterial communities and the diversity of extracellular proteases produced by these bacteria in Antarctic coastal sediments

Summary

Introduction

There is abundant particulate organic material in the sea floor. Bacterial enzymatic activity in sediment is generally considered to be the initial and rate-limiting step in nitrogen recycling [1]. Protease-producing bacteria are important decomposers of sedimentary organic nitrogen (OrgN) because proteins are an important component of the OrgN. We screened 78 proteaseproducing strains from the sediments of the South China Sea and investigated the diversity of both the cultivable proteaseproducing bacteria and their extracellular proteases [3]. It was found that these protease-producing bacterial strains were mainly affiliated with the class Gammaproteobacteria and that their extracellular proteases were serine proteases and metalloproteases. The global sea floor is widespread with various environments; the protease-producing bacteria and their extracellular proteases in different regions may differ in type and quantity

Methods

Results

Conclusion