Bacterial diversity in water from Xifeng Hot Spring in China

Abstract

The Xifeng Hot Spring is one of the eight largest hot springs in China, which is rich in radon gas and sulphur in karst scenery. Little is known about the microbiota structure in the spring. The water was collected from three sites containing the outlet of spring water discharge site (OWD), spring pool for tourist (SPT) and sewage effluent pool (SEP) in the Xifeng Hot Spring and further analyzed by culture-independent technique and culture-dependent method. A total of 57 phyla were identified from the water samples. The dominate phyla at OWD was Bacteroidetes (46.93%), while it was Proteobacteria in both sites of SEP and SPT with relative richness of 61.9% and 94.9%, respectively. Two bacteria, Deinococcus and Hymenobacter, that confirmed to be radiation-resistant, seven sulphur bacteria and three thermophilic bacteria were detected from Xifeng Hot Spring. Furthermore, it was found that genus Flavobacterium was susceptible to environmental change with abundance of 11 ~ 2825 times higher in OWD than the other two groups. Compared bacteria from the OWD group with that from 14 hot springs in six countries, total 94 unique genera bacteria were found out from the Xifeng Hot Spring including four thiometabolism-related bacteria (Propionispira, Desulforegula, Desulfobacter and Desulfococcus) and the thermophilic bacterium (Symbiobacterium). Using microbial culturing and isolation technology, sixteen strains were isolated from the water samples of three sites. The diversity of microbiota was abundant and variable along with the niche changed in conditions and surroundings. It indicated that numbers of valuable bacteria resources could be explored from the special surroundings of Xifeng Hot Spring.

Keywords: Bacterial culturing; Metabolic potential; Microbial diversity; Thermophilic bacteria; Xifeng Hot Spring.

Fig. 1

Location of sampling sites in Xifeng Hot Spring in China. A The Xifeng Hot Spring is located in the southeast of China (red balloon marker). B The sampling site of OWD. OWD is the outlet of spring water discharge site that geothermal water gushes out of Xifeng Hot Spring. C The sampling site of SPT. SPT is the sampling site of a visitor bathing area in Xifeng Hot Spring. D The sampling site of SEP. SEP is the sampling site that sewage discharge of Xifeng Hot Spring

Fig. 2

Alpha and Beta diversities of microbes. A The sample rarefaction measurement indicated the depth of sample sequencing. B The Venn diagram showed the shared and unique OTUs among groups. C PCoA plot was calculated based on distance matrices of bacteria from different groups. The PCOA1 separated SPT samples from both samples from the OWD and SEP, with a relatively fast speed of water at the OWD and the slower flow of water at the SPT and SEP. The PCOA2 then separated the OWD from the SEP group, which might be due to the higher temperature in the OWD and SPT and the lower temperature in the SEP

Fig. 3

The bar plot showed top 10 of the relative abundance percentage in phylum (A) and genera (B) in three sample sites (OWD, SPT, SEP) from Xifeng Hot Spring. The X-axis showed 14 samples from different sites, the Y-axis presented the relative abundance from 0 to 100%

Fig. 4

Evolutionary relationships of isolated strains. The evolutionary relationship was inferred using the neighbour-joining method by MEGA11. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test with 1000 replicates were shown near the branches. The tree was drawn to scale, with branch lengths in the same units as those of the evolutionary distances

Fig. 5

Venn diagram of genus bacteria from hot spring in seven countries. The red petals of the Venn diagram represent the unique bacteria of genus level in OWD sample site of the Xifeng Hot Spring, China (marked in red color). The hot springs in each of the 6 countries are the Tikitere, the Whangapaoa, the Rotokawa, the Parariki stream of New Zealand; the Nakabusa hot spring of Japan; the Deulajhari hot spring, the Puga hot spring, the Chhattisgarh hot spring and the Madhya Pradesh hot spring of India; the Sasso Disano hot spring of Italy; the Sungai Klab hot spring of Malaysia; the Alkaline hot spring, the Great Boiling spring, the Five Sisters 5 hot spring of the United States (USA)