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Insights into the mechanisms of desiccation resistance of the Patagonian PAH ‐degrading strain Sphingobium sp. 22B
Author(s) -
Madueño L.,
Coppotelli B.M.,
Festa S.,
Alvarez H.M.,
Morelli I.S.
Publication year - 2018
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.13742
Subject(s) - trehalose , desiccation , sphingomonas , biology , glycogen , strain (injury) , microbiology and biotechnology , polyhydroxybutyrate , biochemistry , bacteria , botany , gene , 16s ribosomal rna , genetics , anatomy
Aim To analyse the physiological response of Sphingobium sp. 22B to water stress. Methods and Results The strain was grown under excess of carbon source and then subjected to low (60 RH ) and high (18 RH ) water stress conditions for 96 h. Quantification of trehalose, glycogen, polyhydroxybutyrate ( PHB ) and transmission electron microscopy ( TEM ) was studied. Genes linked with desiccation were searched in Sphingobium sp. 22B and Sphingomonas ‘ sensu latu’ genomes and their transcripts were quantified by real‐time PCR . Results showed that, in the absence of water stress, strain 22B accumulated 4·76 ± 1·41% of glycogen, 0·84 ± 1·62% of trehalose and 44·9 ± 6·4% of PHB per cellular dry weight. Glycogen and trehalose were mobilized under water stressed conditions, this mobilization was significantly higher in 60 RH in comparison to 18 RH . Gene treY was upregulated sixfold in 60 RH relative to control condition. TEM and quantification of PHB revealed that PHB was mobilized under 60 RH condition accompanied by the downregulation of the phbB gene. TEM images showed an extracellular amorphous matrix in 18 RH and 60 RH . Major differences were found in the presence of aqpZ and trehalose genes between strain 22B and Sphingomonas genomes. Conclusion Strain 22B showed a carbon conservative metabolism capable of accumulation of three types of endogenous carbon sources. The strain responds to water stress by changing the expression pattern of genes related to desiccation, formation of an extracellular amorphous matrix and mobilization of the carbon sources according to the degree of water stress. Trehalose, glycogen and PHB may have multiple functions in different degrees of desiccation. The robust endowment of molecular responses to desiccation shown in Sphingobium sp. 22B could explain its survival in semi‐arid soil. Significance and Impact of the Study Understanding the physiology implicated in the toleration of the PAH ‐degrading strain Sphingobium sp 22B to environmental desiccation may improve the bioaugmentation technologies in semi‐arid hydrocarbon‐contaminated soils.