Bacterial growth, morphology, and cell component changes in Herbaspirillum sp. WT00C exposed to high concentration of selenate

Abstract

Selenium (Se) is a nonmetallic element of the chalcogens. It is primarily available in natural environments as selenate and selenite oxoanions. Although selenate/selenite reduction in many microbes is widely studied at low concentrations (<50 mM), the effects of high selenate stress on bacterial growth, morphology, and cell components have not yet been studied. In this study, the response of Herbaspirillum sp. WT00C to selenate stress at high concentration is investigated by microbiological and scanning electron microscopy (SEM) techniques as well as proteomic analysis. Bacterial growth was seriously inhibited under high selenate concentrations and its growth‐inhibitory phase was prolonged with the increase of selenate concentrations. More interestingly, this bacterium was able to recover its growth even if the selenate concentration was up to 400 mM. Its growth inhibition period shortened to 6 h when the bacterium growing in 200 mM selenate for 28 h was reinoculated to the Luria‐Bertani medium containing 200 mM selenate. The high concentration of selenate also induces marked changes in the cell dimension and surface roughness, as revealed by SEM, along with compositional changes in the cell wall shown by proteomic analysis. The bacterial growth inhibition results from the marked downregulation of the α‐subunit of DNA polymerase III and RNA helicase, whereas its growth recovery is related to its high antioxidative activities. More NADPH synthesis and the upregulation of thioredoxin reductase and GPx are beneficial for Herbaspirillum sp. WT00C to establish and maintain a balance between oxidant and antioxidant intracellular systems for defending selenate toxicity. This study is an important contribution to understanding why Herbaspirillum sp. WT00C survives in a high concentration of selenate and how the bacterial cells respond physiologically to selenate stress at high concentration.

Multiple exposures to high concentrations of selenate significantly improve selenate tolerability, red elemental selenium (Se0) and selenoprotein biosynthesis in Herbaspirillum camelliae WT00C

“…The strains CT00C and NCT00C displayed 10-fold less expression, whereas the strain NT00C increased 7 folds as compared to the strain WT00C. Less transcription of lpxB gene suggested that the activity of lpxB gene was seriously inhibited by high concentration of selenate, which was in accord with the results observed in the previous study [34] . Nevertheless, the expression of lpxB gene was gradually increased along with the increase of exposure times in selenate as shown in Fig.…”

“…When bacterial cells grew in the medium containing selenate or selenite, red color formation in the culture indicated the generation of red elemental selenium (Se 0 ) [29,33,34] . As shown in Fig.…”

“…We also used the strains NCT00C and WT00C-se [34] (two rounds of forced evolution) to produce red elemental selenium via fermentation in LB broth containing 200 mM selenate. The yields of pure elemental selenium gave 1028 mg/L for the strain NCT00C and 560 mg/L for the strainWT00C-se.…”

“…1. 8 genes (mdh, ligK, pntA, iolA, ghrA, gluC, mmsB, argC) thought to be related with selenate tolerance [34] were also examined. In addition, the expression of lpxB gene encoding lipid-Adisaccharide synthase [EC 2.4.1.182] was incidentally tested.…”

Analysis of Threshold Change of Tumor Mutation Burden in Gastric Cancer

“…Surgery can remove the lesion tissue, prolong the life of patients, and quickly improve their symptoms [5]. However, due to the lack of effective evaluation methods in perioperative period of some GC patients, the long-term prognosis of patients is relatively long [6]. Tumor mutation burden (TMB) is defined as the total number of somatic coding errors, base substitutions, gene insertion, or deletion errors detected per million bases, which can be obtained by the NGS method.…”