Changes in the bacterial populations of the highly alkaline saline soil of the former lake Texcoco (Mexico) following flooding

Abstract

Flooding an extreme alkaline-saline soil decreased alkalinity and salinity, which will change the bacterial populations. Bacterial 16S rDNA libraries were generated of three soils with different electrolytic conductivity (EC), i.e. soil with EC 1.7 dS m(-1) and pH 7.80 (LOW soil), with EC 56 dS m(-1) and pH 10.11 (MEDIUM soil) and with EC 159 dS m(-1) and pH 10.02 (HIGH soil), using universal bacterial oligonucleotide primers, and 463 clone 16S rDNA sequences were analyzed phylogenetically. Library proportions and clone identification of the phyla Proteobacteria, Actinobacteria, Acidobacteria, Cyanobacteria, Bacteroidetes, Firmicutes and Cloroflexi showed that the bacterial communities were different. Species and genera of the Rhizobiales, Rhodobacterales and Xanthomonadales orders of the alpha- and gamma-subdivision of Proteobacteria were found at the three sites. Species and genera of the Rhodospirillales, Sphingobacteriales, Clostridiales, Oscillatoriales and Caldilineales were found only in the HIGH soil, Sphingomonadales, Burkholderiales and Pseudomonadales in the MEDIUM soil, Myxococcales in the LOW soil, and Actinomycetales in the MEDIUM and LOW soils. It was found that the largest diversity at the order and species level was found in the MEDIUM soil as bacteria of both the HIGH and LOW soils were found in it.

A meta-analysis of the publicly available bacterial and archaeal sequence diversity in saline soils

“…In one study, however, it was found that although Actinobacteria was represented in both medium and low saline soils, it was absent in extremely high saline soils (Valenzuela-Encinas et al 2009). The actinobacterial sequences were assigned to the subclasses Actinobacteridae, Acidimicrobidae, Nitriliruptoridae, and Rubrobacteridae.…”

“…The dominant class within the Proteobacteria was Gammaproteobacteria, followed by Alphaproteobacteria and Deltaproteobacteria. In studies of soils from the former lake Texcoco, Valenzuela-Encinas et al (2009) showed that the dominant class of Proteobacteria in both high (158 dS m -1 ) and low (0.65 dS m -1 ) saline soils was Gammaproteobacteria, whereas in medium (56 dS m -1 ) saline soils the dominant class was Alphaproteobacteria. Furthermore, Deltaproteobacteria was present in both high and low saline soils, but absent in medium saline soils (Valenzuela-Encinas et al 2009).…”

“…The bacterial and archaeal communities vary in soils with different salt concentrations (Valenzuela-Encinas et al 2009). Although the dataset contains sequences recovered from a wide array of studies, the beta diversity could not be determined because some studies submitted sequences to databases without published information on the soil properties.…”

“…In most cases only a few soil samples of a single specific saline system, or a small number of cloned sequences or DGGE bands, have been investigated and analyzed. Some studies have focused only one particular microbial group such as Archaea (Valenzuela-Encinas et al 2009;Youssef et al 2012) or Actinobacteria (Singh et al 2012). Numerous sequences recovered from saline soils are available from the GenBank, but many of these are largely overlooked because they are not published in the literature.…”

Global Biogeography and Quantitative Seasonal Dynamics of Gemmatimonadetes in Soil

“…Percent soil moisture (⍜) was determined gravimetrically after oven drying. Soil pH was determined by combining 10 g soil with 10 ml deionized H 2 O. Nitrogen and carbon content were determined by using dry combustion on a Carlo-Erba C/N analyzer, and phosphorus (6,14), alpine hyper arid soils (9), hot desert (8,39,47), alpine tundra (37), Antarctic peninsula/coastal (6, 45), semiarid soils (1, 26, 32), prairies/grasslands (12, 41), pasture (22), crop agriculture (7,22,29,41,50), temperate forest (17,22,29,30,41), tropical forest (13), moist acidic tundra (5), and freshwater sediments (27,48 . Fibrobacter succinogenes was used as an outgroup.…”