Abstract
Psychrobacter sp. DAB_AL32B, originating from Spitsbergen island (Arctic), carries the large plasmid pP32BP2 (54,438 bp). Analysis of the pP32BP2 nucleotide sequence revealed the presence of three predicted phenotypic modules that comprise nearly 30% of the plasmid genome. These modules appear to be involved in fimbriae synthesis via the chaperone-usher pathway (FIM module) and the aerobic and anaerobic metabolism of carnitine (CAR and CAI modules, respectively). The FIM module was found to be functional in diverse hosts since it facilitated the attachment of bacterial cells to abiotic surfaces, enhancing biofilm formation. The CAI module did not show measurable activity in any of the tested strains. Interestingly, the CAR module enabled the enzymatic breakdown of carnitine, but this led to the formation of the toxic by-product trimethylamine, which inhibited bacterial growth. Thus, on the one hand, pP32BP2 can enhance biofilm formation, a highly advantageous feature in cold environments, while on the other, it may prevent bacterial growth under certain environmental conditions. The detrimental effect of harboring pP32BP2 (and its CAR module) seems to be conditional, since this replicon may also confer the ability to use carnitine as an alternative carbon source, although a pathway to utilize trimethylamine is most probably necessary to make this beneficial. Therefore, the phenotype determined by this CAR-containing plasmid depends on the metabolic background of the host strain.
Highlights
IntroductionBacteria of the genus Psychrobacter (class Gammaproteobacteria) are Gram-negative, non-motile, psychrotolerant, and halotolerant coccobacilli [1,2,3]
Bacteria of the genus Psychrobacter are Gram-negative, non-motile, psychrotolerant, and halotolerant coccobacilli [1,2,3]
DAB_AL32B [22] was insufficient to permit the assembly of the complete nucleotide sequence of plasmid pP32BP2
Summary
Bacteria of the genus Psychrobacter (class Gammaproteobacteria) are Gram-negative, non-motile, psychrotolerant, and halotolerant coccobacilli [1,2,3]. The majority of strains are recognized as halotolerant or halophilic, since they are able to grow in the presence of NaCl at concentrations of up to 25% (w/v) These bacteria tolerate high concentrations of potassium and magnesium [2,12,13,14]. The increased occurrence of Psychrobacter spp. in some environments may be linked to the presence of various harmful xenobiotics (e.g., diverse hydrocarbons), which can be utilized as carbon sources [15,16]. Such metabolic properties with adaptive value are often determined by mobile genetic elements, including plasmids. Available reports concerning the role of plasmids in the adaptation of psychrophilic and psychrotolerant bacteria to extreme polar conditions are limited and rather fragmentary (e.g., [17,18,19,20])
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