Lag period of14CO2evolution from dioctyl sulpho[2,3-14C]succinate in relation to adaptation of bacterium, Comamonas terrigena, to dialkyl esters of sulphosuccinate

Isolates of Comamonas spp. exhibiting catalase and peroxidase activities and diversity of their responses to oxidative stress

For survival isolates of Comamonas testosteroni CCM 1931, C. testosteroni K3, C. terrigena N3H or N1C and C. terrigena CCM 2409, selected largely from polluted environments, the production of catalase and dianisidine-peroxidase activity was important. Electrophoretic resolution of cell-free extracts of aerobically grown strains in Luria-Bertani medium during the exponential phase revealed distinctive expression of catalatic and peroxidatic activities detected with 3,3'-diaminobenzidine tetrahydrochloride (DAB). The protection of isolates from 20 or 40 mM H(2)O(2) stress was characterized with a considerable diversity in catalase and peroxidase responses that resulted from hydroperoxidase's variant of original isolates, indicating also a selective pressure of environment. Results indicate catalase to be important for adaptation of cultures to high concentration of 60mM H(2)O(2). The greatest appreciable differences in sensitivity to toxic effect of H(2)O(2) (20 or 40 mM) treatment between individual isolates and their adapted variants during the growth were observed until the middle of exponential phase. Isolates exhibited diversity in catalases responses to possible contaminants o-or p-phenylenediamine (PDA) as well. Only positional isomer p-PDA (1 or 2mM) stimulated catalase activity unlike from isomer o-PDA in C. terrigena N3H cells. The study can contribute to understanding of bacterial antioxidative enzymatic responses in the presence of possible physiological stress resulting mainly from environmental pollutants.

Molecular diversity of katG genes in the soil bacteria Comamonas

Three complete katG genes coding for bifunctional catalase-peroxidases (KatGs) from the beta-proteobacterium Comamonas terrigena and two related strains of Comamonas testosteroni have been cloned and sequenced. Catalase-peroxidases are unique bifunctional enzymes known to be expressed in these soil bacteria in response to environmental and/or oxidative stress. The evolutionary and structural diversity of these enzymes is investigated based on multiple sequence alignment and comprehensive phylogenetic analysis. The reconstructed phylogenetic tree and well-known structure-function relationships were applied to inspect the conservation of essential residues. Observed diversity is discussed with respect to the fact that KatGs are distinctive gene-duplicated peroxidases comprising a N-terminal (enzymatically active) and a C-terminal (heme-less) domain. The unique promoter motifs regulating katG transcription in four strains of Comamonas were detected and compared with E. coli katG promoter. The relationship between the promoter sequences and the corresponding expression levels was analyzed. A significant difference in heat shock-inducible catalatic and peroxidatic activities between E. coli K12 and Comamonas terrigena & testosteroni strains was observed. The peculiar variability in gene-coding sequences appears to be more significant for such activity output among Comamonas strains than differences in their promoter regions. The functional role of observed increased diversity in the C-terminal domain is discussed with respect to potential modification of catalytic features at the N-terminal domain that could be relevant for these soil bacteria to cope with stressors.

ELECTRONIC SUPPLEMENTARY MATERIAL

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Screening of bacterial isolates from polluted soils exhibiting catalase and peroxidase activity and diversity of their responses to oxidative stress

For the survival of individual isolates of gram-negative bacteria Pseudomonas putida, Achromobacter xylosoxidans, and the gram-positive bacterium Bacillus megaterium, in an environment polluted with crude oil products, the production of catalases exhibiting both catalase and dianisidine-peroxidase activity is important. Electrophoretic resolution of cell-free extracts of aerobically grown strains in Luria-Bertani medium during exponential phase revealed distinctive expression of catalatic and peroxidatic activities detected with 3,3'-diaminobenzidine tetrahydrochloride. A considerable diversity in microbial catalase and peroxidase responses to 20 or 40 mM H(2)O(2) stress, resulted from hydroperoxidase's variant of original isolates, indicating an environmental selective pressure. However, catalase was important for the adaptation of cultures to high concentration of 60 mM H(2)O(2). Appreciable differences in the sensitivity to toxic effect of H(2)O(2) (20 or 40 mM) treatment between individual isolates and their adapted variants during growth were observed until the middle of exponential phase, but they were insignificant at the entry to stationary phase. Isolates also exhibited a considerable diversity in catalases responses to phenolic contaminants 1 and 2 mM o- or p-phenylenediamine. Catalase activity of bacterium P. putida was visibly stimulated only by p-phenylenediamine and not by its positional isomer o-PDA. This study contributes to a better understanding of the role catalases play in bacterial responses to a polluted environment.

The Expression and Diversity of Catalases in Isolates of Genus Comamonas in Response to the Oxidative Stress of a Polluted Environment

We have evaluated the role of monofunctional heme-containing catalase encoded by cat-1 gene from the soil bacterium Comamonas terrigena N3H in the response to various forms of oxidative stress. Our results indicate that this constitutively expressed catalase represents the major source for the defence of Comamonas terrigena cells against toxic peroxides but the cells can express also a second form of catalase that is bigger and its regulation is probably more complicated. The sequence analysis confirmed the presence of highly conserved catalase sequence motifs in two environmental strains of Comamonas terrigena but in those strains that were not exposed to oxidative stress, no such sequence motif could be detected. The results obtained underline the importance of catalase expression in the defence mechanism against oxidative stress in bacterial cells.

Production of catalases by Comamonas spp. and resistance to oxidative stress

Bacterial isolates Comamonas terrigena N3H (from soil contaminated with crude oil) and C. testosteroni (isolated from the sludge of a wastewater treatment plant), exhibit much higher total catalase activity than the same species from laboratory collection cultures. Electrophoretic resolution of catalases revealed only one corresponding band in cell-free extracts of both C. testosteroni cultures. Isolates of C. terrigena N3H exhibited catalase-1 and catalase-2 activity, whereas in the collection culture C. terrigena ATCC 8461 only catalase-1 was detected. The environmental isolates exhibited much higher resistance to exogenous H2O2 (20, 40 mmol/L) than collection cultures, mainly in the middle and late exponential growth phases. The stepwise H2O2-adapted culture of C. terrigena N3H, which was more resistant to oxidative stress than the original isolate, exhibited an increase of catalase and peroxidase activity represented by catalase-1. Pretreatment of cells with 0.5 mmol/L H2O2 followed by an application of the oxidative agent in toxic concentrations (up to 40 mmol/L) increased the rate of cell survival in the original isolate, but not in the H2O2-adapted variant. The protection of bacteria caused by such pretreatment corresponded with stimulation of catalase activity in pretreated culture.