Spatio-Temporal Variation of the Bacterial Communities along a Salinity Gradient within a Thalassohaline Environment (Saline di Tarquinia Salterns, Italy)

Abstract

The “Saline di Tarquinia” salterns have been scarcely investigated regarding their microbiological aspects. This work studied the structure and composition of their bacterial communities along the salinity gradient (from the nearby sea through different ponds). The communities showed increasing simplification of pond bacterial diversity along the gradient (particularly if compared to those of the sea). Among the 38 assigned phyla, the most represented were Proteobacteria, Actinobacteria and Bacteroidetes. Differently to other marine salterns, where at the highest salinities Bacteroidetes dominated, preponderance of Proteobacteria was observed. At the genus level the most abundant taxa were Pontimonas, Marivita, Spiribacter, Bordetella, GpVII and Lentibacter. The α-diversity analysis showed that the communities were highly uneven, and the Canonical Correspondence Analysis indicated that they were structured by various factors (sampling site, sampling year, salinity, and sampling month). Moreover, the taxa abundance variation in relation to these significant parameters were investigated by Generalized Linear Models. This work represents the first investigation of a marine saltern, carried out by a metabarcoding approach, which permitted a broad vision of the bacterial diversity, covering both a wide temporal span (two years with monthly sampling) and the entire salinity gradient (from the nearby sea up to the crystallisation ponds).

Persistence of Enterobacteriaceae Drawn into a Marine Saltern (Saline di Tarquinia, Italy) from the Adjacent Coastal Zone

“…All parameters are reported in Table S1. Sample collection, measurement, and the determination of environmental parameters were carried out as reported by Gorrasi et al [57].…”

“…The primers used, 783F (5′-CAGGATTAGATACCC) and 1046R (5′-CGACRRCCATGCANCACCT) [62,63], were modified by adding external barcodes to allow the parallel processing of multiple samples. The strategy and related protocols used to prepare the libraries have already been described in detail by Gorrasi et al [57].…”

“…100 shallow interconnected ponds that allow the establishment of an increasing salinity gradient, starting from the water pumped from the nearby sea which is transferred through low-salinity ponds (concentrators), to ponds where salt precipitation occurs (crystallisers) [49]. Some studies have been carried out to investigate the microbial diversity of the site [50][51][52][53][54][55][56][57]. The site algal microflora was studied both from the taxonomic point of view [50,56] and for some aspects regarding their pigment production, which is particularly interesting at the biotechnological level [52,55].…”

“…The ST bacterial diversity showed increasing simplification along the gradient according to salinity increases. Moreover, the communities were structured by various factors: salinity, sampling site, and sampling year and month [57] However, investigations related to some particular bacterial groups are quite scarce. The only study considering a specific bacterial group was focused on inspecting the presence of Vibrio within the ST system, which was demonstrated to be a possible reservoir for members of this genus even if at very low levels of abundance [49].…”

Polyextremophilic Chitinolytic Activity by a Marine Strain (IG119) of Clonostachys rosea

“…For example, in the deep ocean microorganisms are subject to high hydrostatic pressure combined with low or high temperature or to high salinity and alkaline pH. Besides, in various marine transition areas (intertidal zones, estuaries and marine salterns), they are submitted to sudden and repeated variations of temperature and salinity [ 1 , 2 , 3 ].…”