Microbial community composition of Tirez lagoon (Spain), a highly sulfated athalassohaline environment

Abstract

Background: The aim was to study the seasonal microbial diversity variations of an athalassohaline environment with a high concentration of sulfates in Tirez lagoon (La Mancha, Spain). Despite the interest in these types of environments there is scarce information about their microbial ecology, especially on their anoxic sediments.

Results: We report the seasonal microbial diversity of the water column and the sediments of a highly sulfated lagoon using both molecular and conventional microbiological methods. Algae and Cyanobacteria were the main photosynthetic primary producers detected in the ecosystem in the rainy season. Also dinoflagelates and filamentous fungi were identified in the brines. The highest phylotype abundance in water and sediments corresponded to members of the bacterial phylum Proteobacteria, mainly of the Gamma- and Alphaproteobacteria classes. Firmicutes and Actinobacteria were isolated and identified in Tirez brines and sediment samples. Halophilic sulfate reducing Deltaproteobacteria were also detected (Desulfohalobium).

Conclusions: Important differences have been found in the microbial diversity present in the Tirez water column and the sediments between the wet and dry seasons. Also the Tirez lagoon showed a high richness of the bacterial Alpha- and Deltaproteobacteria, Bacteroidetes, Firmicutes, Actinobacteria and for the archaeal Euryarchaeota.

Figure 1

Chemical composition compared from diverse hypersaline lakes following the Eugster and Hardy criteria[8]. Dead Sea, brine [10], Sea water [2], Maras Saltern, brine [11], Qingai Alkali Lake, brine [12], Mono Lake, brine [13], Chaka Lake, brine [14], Atacama Lake, brine [15], Salt Lake, brine [10], Tirez Lagoon, sediment and brine from present study (multiple samples represent different depths or different seasons), Cuatro Cienengas Basin, brine [16], Discovery Basin, brine [17], L’Atalante, Thetis and Bannock basins [18] and Silver Lake playa lake [19].

Figure 2

Map showing the Tirez lagoon sampling site (UTM: 4377309, 46982) in La Mancha region (Spain).

Figure 3

Phylogenetic tree based on 16S rRNA sequences bacterial clones from Tirez water column and sediment from the rainy season. The tree topology was constructed with Mr. Bayes. Percentage of probability support in main nodes is indicated if ≥80%. The scale bar represents expected changes per site. Highlighted phylotypes in bold type are prefixed by Rw (rainy water), Rs (rainy sediment), Dw (dry water) and Ds (dry sediment) and followed by cb (clone bacteria) and ID number. The access number and the number of collapsed phylotypes assigned to OTU with ≥97% identity is indicated in parenthesis.

Figure 4

Phylogenetic tree based on 16S rRNA sequences archaeal clones from Tirez water column and sediments from the rainy and dry seasons. The tree topology was constructed with Mr. Bayes. Percentage of probability support in main nodes is indicated if ≥80%. The scale bar represents expected changes per site. Highlighted phylotypes in bold type are prefixed by Rw (rainy water), Rs (rainy sediment), Dw (dry water) and Ds (dry sediment) and followed by cb (clone bacteria) and ID number. The number of collapsed phylotypes assigned to OTU with ≥97% identity is indicated in parenthesis.

Figure 5

Denaturing gradient gel electrophoresis (DGGE) band patterns with specific primers for Bacteria 16S rRNA gene fragment in sediment (a) and water (b) samples. Band patterns resulted from 30-70% (a) and 40-70% (b) denaturing gradients. Sediment patterns are D for dry and R for rainy seasons, and their respective depths: 1) surface (0–5 cm), 2) 5–15 cm, 3) 15–25 cm and 4) 25–35 cm. The water DGGE pattern is derived from rainy samples. Bands with numbers were excised from the gels and sequenced. Sequences were identified by the prefix describing the community sampled (Rw, Rs, Dw and Ds), technique used (db for DGGE and bacteria) and ID number.

Figure 6

Denaturing gradient gel electrophoresis (DGGE) band patterns obtained with specific primers for 16S rRNA gene fragments; from Archaea in sediment samples (a) and Deltaproteobacteria in cultures (b). The band patterns resulted from 40-70% (a) and 30-50% (b) denaturing gradients. The patterns are from two different seasons, rainy (R) and dry (D), and their respective depths are: 1) surface (0–5 cm), 2) 5–15 cm, 3) 15–25 cm and 4) 25–35 cm. Bands with numbers were excised from the gels and sequenced. Sequences were identified by the prefix describing the community sampled (Rw, Rs, Dw and Ds), technique used (da for DGGE and archaea) and ID number.