Abstract
With the advantages of wide distribution, fast growth, and broad metabolic spectrum to organic carbon compounds, Vibrio may play an important role in organic carbon cycling. However, the ecological roles of Vibrio in many marine environments have not been explored. Here, the world’s deepest ‘blue hole’, the Sansha Yongle Blue Hole (SYBH) in the South China Sea, which is a geographically semi-enclosed environment featuring unique chemical characters, was investigated. The abundance, diversity and carbon source utilization capability of Vibrio were studied by quantification and high-throughput sequencing of Vibrio specific 16S rRNA genes and cultivation methods. The abundance of Vibrio in water column of the SYBH ranged from 3.78 × 104 to 7.35 × 106 16S rRNA gene copies L−1. Free-living Vibrio was more abundant than particle-associated Vibrio (~ 1.20 × 106 versus~ 2.68 × 105 gene copies L−1), indicating that Vibrio prefers a free-living life style. The Vibrio assemblages showed clear vertical stratification and could be divided into three groups: aerobic-transition, middle anaerobic and bottom anaerobic zones. Dissolved oxygen (DO), temperature, pH and salinity were the main environmental factors affecting the abundance and community composition. Cultivated Vibrio demonstrated a degrading capability to various macromolecular substrates, including starch, Tween 20/40/80, DNA, gelatin, alginate, casein, chitin, lecithin, κ-carrageenan, mannan, xylan and hyaluronic acid. This suggests that Vibrio could produce a variety of highly active extracellular enzymes. Our study provides new insights into the distribution pattern and possible role in carbon cycle of Vibrio in the unique environment of a ‘blue hole’.
Highlights
The genus Vibrio is a group of gram-negative bacteria belonging to the Vibrionaceae family of the Gammaproteobacteria, which are usually mesophilic and heterotrophic motile rods (Thompson et al 2004a)
PH, Dissolved oxygen (DO) and NO2− decreased with depth, whereas salinity, NH4+, PO43− and SiO32− showed opposite trends (Yao et al 2018)
DO was considered to be the main cause for these changes, while the other parameters, such as NH4+, NO3− and PO43−, co-varied with DO (Yao et al 2018)
Summary
The genus Vibrio is a group of gram-negative bacteria belonging to the Vibrionaceae family of the Gammaproteobacteria, which are usually mesophilic and heterotrophic motile rods (Thompson et al 2004a). Extended author information available on the last page of the article even including deep-sea hydrothermal vents and sediments at a depth of more than 6000 m, and seawater at a depth of 10,500 m in the Mariana Trench (Hasan et al 2015; Hsieh et al 2008; Li et al 1999; Liu et al 2019). The genus Vibrio contains more than 110 species, many of which are known as causative agents of foodborne related illnesses, which have a huge impact on public health and management (Lee and Raghunath 2018; Letchumanan et al 2015; Pruzzo et al 2005). The major pathogenic Vibrio species include Vibrio cholerae, V. parahaemolyticus and V. vulnificus (Letchumanan et al 2016)
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