Diversity of cultivable protease-producing bacteria and their extracellular proteases associated to scleractinian corals

Abstract

Protease-producing bacteria play a vital role in degrading organic nitrogen in marine environments. However, the diversity of the bacteria and extracellular proteases has seldom been addressed, especially in communities of coral reefs. In this study, 136 extracellular protease-producing bacterial strains were isolated from seven genera of scleractinian corals from Luhuitou fringing reef, and their protease types were characterized. The massive coral had more cultivable protease-producing bacteria than branching or foliose corals. The abundance of cultivable protease-producing bacteria reached 106 CFU g−1 of coral. Phylogenetic analysis of 16S rRNA gene sequences revealed that the isolates were assigned to 24 genera, from which 20 corresponded to the phyla Firmicutes and Proteobacteria. Bacillus and Fictibacillus were retrieved from all coral samples. Moreover, Vibrio and Pseudovibrio were most prevalent in massive or foliose coral Platygyra and Montipora. In contrast, 11 genera were each identified in only one isolate. Nearly all the extracellular proteases from the bacteria were serine proteases or metalloproteases; 45.83% of isolates also released cysteine or aspartic proteases. These proteases had different hydrolytic ability against different substrates. This study represents a novel insight on the diversity of cultivable protease-producing bacteria and their extracellular proteases in scleractinian corals.

High Diversity of β-Glucosidase-Producing Bacteria and Their Genes Associated with Scleractinian Corals

“…Previous studies in related fields have demonstrated that the activity and diversity of β-glucosidases are significantly driven by shifts in the bacterial community structure, rather than by simple induction of enzyme expression during coastal phytoplankton blooms [ 35 ] and soil aggregation [ 39 ]. Culture-dependent methods have revealed the presence of numerous extracellular enzyme-producing microorganisms in corals [ 16 ]. In our study, 87 cultivable β-glucosidase-producing bacteria obtained from coral were divided into 17 genera and classified into Proteobacteria and Firmicutes, except for four isolates belonging to Actinobacteria.…”

“…Many studies support the notion that the microbiome of corals is distinct from that of the overlying seawater, and that bacterial communities supported by corals fluctuate with the season [ 9 , 11 ] and are host-specific [ 12 , 13 ], geographically consistent [ 6 ], and physiologic [ 14 , 15 ]. Nevertheless, the number of bacterial strains isolated from coral is very small [ 9 , 16 ], and their specific physiological roles have not been fully elucidated.…”

Community Structure of Protease-Producing Bacteria Cultivated From Aquaculture Systems: Potential Impact of a Tropical Environment

“…In turn, the dissolved organic matter can be transformed into nitrogen gas by ammonification, nitrification, and denitrification. Bacteria play key roles in these processes by secreting degradation enzymes ( Olson and Lesser, 2013 ; Su et al, 2020 ).…”

“…Protease-producing bacteria as the main degraders of organic matter can effectively hydrolyze the organic matter into peptides and amino acids by secreting extracellular proteases ( Su et al, 2020 ). As we all know, peptides and amino acids are essential for subsequent catabolism of organisms.…”

“…As we all know, peptides and amino acids are essential for subsequent catabolism of organisms. Reportedly, protease-producing bacteria could not only improve protein digestibility and growth of the host, but also reduce organic pollutants in aquaculture ( Shi et al, 2016 ; Amin, 2018 ; Su et al, 2020 ). Protease-producing bacteria that belong to four major phyla, Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes, have been identified, which are dominated by Bacillus , Pseudomonas , and Pseudoalteromonas genera ( Su et al, 2020 ).…”