Study of Bacterial Community Composition and Correlation of Environmental Variables in Rambla Salada, a Hypersaline Environment in South-Eastern Spain

Abstract

We studied the bacterial community in Rambla Salada in three different sampling sites and in three different seasons and the effect of salinity, oxygen, and pH. All sites samples had high diversity and richness (Rr > 30). The diversity indexes and the analysis of dendrograms obtained by DGGE fingerprint after applying Pearson's and Dice's coefficient showed a strong influence of sampling season. The Pareto-Lorenz (PL) curves and Fo analysis indicated that the microbial communities were balanced and despite the changing environmental conditions, they can preserve their functionality. The main phyla detected by DGGE were Bacteroidetes (39.73%), Proteobacteria (28.43%), Firmicutes (8.23%), and Cyanobacteria (5.14%). The majority of the sequences corresponding to uncultured bacteria belonged to Bacteroidetes phylum. Within Proteobacteria, the main genera detected were Halothiobacillus and Roseovarius. The environmental factors which influenced the community in a higher degree were the salinity and oxygen. The bacteria belonging to Bacteroidetes and Proteobacteria were positively influenced by salinity. Nevertheless, bacteria related to Alpha- and Betaproteobacteria classes and phylum Firmicutes showed a positive correlation with oxygen and pH but negative with salinity. The phylum Cyanobacteria were less influenced by the environmental variables. The bacterial community composition of Rambla Salada was also studied by dilution-to-extinction technique. Using this method, 354 microorganisms were isolated. The 16S sequences of 61 isolates showed that the diversity was very different to those obtained by DGGE and with those obtained previously by using classic culture techniques. The taxa identified by dilution-to-extinction were Proteobacteria (81.92%), Firmicutes (11.30%), Actinobacteria (4.52%), and Bacteroidetes (2.26%) phyla with Gammaproteobacteria as predominant class (65.7%). The main genera were: Marinobacter (38.85%), Halomonas (20.2%), and Bacillus (11.2%). Nine of the 61 identified bacteria showed less than 97% sequence identity with validly described species and may well represent new taxa. The number of bacteria in different samples, locations, and seasons were calculated by CARD-FISH, ranging from 54.3 to 78.9% of the total prokaryotic population. In conclusion, the dilution-to-extinction technique could be a complementary method to classical culture based method, but neither gets to cultivate the major taxa detected by DGGE. The bacterial community was influenced significantly by the physico-chemical parameters (specially the salinity and oxygen), the location and the season of sampling.

Transient Dynamics of Archaea and Bacteria in Sediments and Brine Across a Salinity Gradient in a Solar Saltern of Goa, India

“…Like several other salterns and hypersaline environments, Siridao salterns support diverse communities of phylotypes belonging to Bacteroidetes and Gammaproteobacteria (Sørensen et al, 2005;Baati et al, 2011;Zhang et al, 2016). The occurence of Alphaproteobacteria, Betaproteobacteria and Firmicutes decreased with increasing salinity which was consistent with the results obtained by Oueriaghli et al (2018). A study carried out in the same salterns under investigation, employing DGGE had recovered sequences affiliated with Gammaproteobacteria, supporting their importance at Siridao salterns (Mani et al, 2015).…”

“…On the other hand, though Spiribacter could tolerate wide salinity fluctuations (0-2 M NaCl), its growth peaks at very specific salinity (0.8 M NaCl) making it difficult to flourish in highly fluctuating salinities ( León et al, 2018 ). Few studies carried out in the salterns of Chile, Argentina, Poland, and Spain have also reported the absence or low incidence of Salinibacter ( Kalwasińska et al, 2018 ; Mora-Ruiz et al, 2018 ; Oueriaghli et al, 2018 ). Further, considering the absence of dominant archaeal phylotype of Haloquadratum and bacterial phylotypes such as Salinibacter and Spiribacter , we are in complete agreement with the views drawn by Gomariz et al (2015) that solar salterns, despite being called ‘steady-state’ systems, undergo various microbial fluctuations at similar salinities and therefore general conclusions should be drawn with caution.…”

Isolation and diversity of sediment bacteria in the hypersaline aiding lake, China

“…Halophiles thrive in hypersaline niches and have potential applications in biotechnology [1,2]. Microbial diversity in most hypersaline environments is often studied using culture-dependent and -independent methods [3][4][5][6][7]. Previous studies have shown that the taxonomic diversity of microbial populations in terrestrial saline and hypersaline environments is relatively low [8,9].…”

Population structure determined by comparative amplicon gene sequencing in biofilm and planktonic bacterial communities from pesticide-contaminated water

“…However, microbial diversity is high and poorly elucidated by culture techniques, even with different types of culture media, since a large percentage of these microorganisms are nonculturable [7,8]. Therefore, it is necessary to create new research tools that allow the characterization of microbiological biodiversity, i.e., molecular microbial ecology, through the use of high-throughput sequencing technologies with the aid of bioinformatics techniques for data analysis [1,9–11].…”