Endothiovibrio diazotrophicus gen. nov., sp. nov., a novel nitrogen-fixing, sulfur-oxidizing gammaproteobacterium isolated from a salt marsh

Abstract

A novel non-phototrophic, marine, sulfur-oxidizing bacterium, strain S-1T, was isolated from a coastal salt marsh in Massachusetts, USA. Cells are Gram-stain-negative vibrios motile by means of a single polar unsheathed flagellum. S-1T is an obligate microaerophile with limited metabolic capacity. It grows chemolithoautotrophically utilizing sulfide and thiosulfate as electron donors, converting these compounds to sulfate, and the Calvin-Benson-Bassham cycle for carbon fixation. Cells of S-1T did not grow on any of a large number of organic carbon sources and there was no evidence for chemoorganoheterotrophic growth. Cells produced internal sulfur globules during growth on sulfide and thiosulfate. S-1T is strongly diazotrophic, as demonstrated by 15N2 fixation and acetylene reduction activity by cells when a fixed nitrogen source is absent from the growth medium. The marine nature of this organism is evident from its ability to grow in 10 to 100 % artificial seawater but not at lower concentrations and NaCl alone cannot substitute for sea salts. The major cellular fatty acids are C16 : 1ω7c, C16 : 0, and C18 : 1ω7c. Phosphatidylethanolamine and phosphatidylglycerol are the major polar lipids. Q8 is the only respiratory quinone. S-1T genomic DNA has a G+C content of 67.6 mol%. Based on its 16S rRNA gene sequence, S-1T shows the closest phylogenetic relationship to non-phototrophic species within the family Thioalkalispiraceae of the class Gammaproteobacteria. The name Endothiovibrio diazotrophicus is proposed for this organism, with S-1T as the type strain (ATCC BAA-1439T=JCM 17961T).

Biogeographic distribution of autotrophic bacteria was more affected by precipitation than by soil properties in an arid area

“…The general occurrence of these cbbL taxa in the southern region and previous studied crop soils suggests their important roles in soil C and N cycles in agricultural soils. Sterolibacteriaceae, Acidithiobacillaceae, Thioalkalispiraceae and Thiobacillaceae are involved in nitrogen and/or sulfur cycling ( Aroca et al, 2007 ; Watanabe et al, 2014 ; Bazylinski et al, 2017 ), suggesting that these cbbM taxa might play an important role in soil functional processes (such as C and N and sulfur cycling) in the northern forest/grassland soils. The generalist taxa in the Chinese Loess Plateau were mainly chemolithoautotrophic bacteria, which might be due to the soil sampling depth 0–10 cm; a shallow soil layer, e.g., 0–1 cm, might get a higher proportion of phototrophic autotrophs such as Cyanobacteria ( Zhao et al, 2018 ).…”

“…Thus, autotrophic microorganisms are ubiquitous in terrestrial ecosystems. Additionally, autotrophic bacteria also play critical roles in soil element cycling such as nitrogen and sulfur cycling ( Aroca et al, 2007 ; Bazylinski et al, 2017 ). Therefore, autotrophic microorganisms may play important roles in regulating ecosystem functions.…”