Identification and characterization of VapBC toxin-antitoxin system in Bosea sp. PAMC 26642 isolated from Arctic lichens

• Published in: RNA (Cambridge) Vol. 27; no. 11; pp. 1374 - 1389
• Main Authors: Jeon, Hyerin, Choi, Eunsil, Hwang, Jihwan
• Format: Journal Article
• Language: English
• Published: United States Cold Spring Harbor Laboratory Press 01-11-2021
• Subjects: Antitoxins - genetics; Antitoxins - metabolism; Bacterial Proteins; Bacterial Toxins - genetics; Bacterial Toxins - metabolism; Biodegradation; Bradyrhizobiaceae - genetics; Bradyrhizobiaceae - growth & development; Bradyrhizobiaceae - isolation & purification; Bradyrhizobiaceae - metabolism; E coli; Escherichia coli; Escherichia coli - genetics; Escherichia coli - growth & development; Escherichia coli - metabolism; Gene Expression Regulation, Bacterial; Genomes; Lichens; Lichens - physiology; Low temperature; Northern blotting; Operon; Polymerase chain reaction; Prokaryotes; Promoter Regions, Genetic; RNA, Transfer, Met - metabolism; Toxin-Antitoxin Systems - genetics; Arctic region; extremophile; endoribonuclease; toxin–antitoxin system; Bosea; VapBC
• ISSN: 1355-8382; 1469-9001
• DOI: 10.1261/rna.078786.121

Toxin-antitoxin (TA) systems are genetic modules composed of a toxin interfering with cellular processes and its cognate antitoxin, which counteracts the activity of the toxin. TA modules are widespread in bacterial and archaeal genomes. It has been suggested that TA modules participate in the adaptation of prokaryotes to unfavorable conditions. The
sp. PAMC 26642 used in this study was isolated from the Arctic lichen
sp. There are 12 putative type II TA loci in the genome of
sp. PAMC 26642. Of these, nine functional TA systems have been shown to be toxic in
The toxin inhibits growth, but this inhibition is reversed when the cognate antitoxin genes are coexpressed, indicating that these putative TA loci were bona fide TA modules. Only the BoVapC1 (AXW83_01405) toxin, a homolog of VapC, showed growth inhibition specific to low temperatures, which was recovered by the coexpression of BoVapB1 (AXW83_01400). Microscopic observation and growth monitoring revealed that the BoVapC1 toxin had bacteriostatic effects on the growth of
and induced morphological changes. Quantitative real time polymerase chain reaction and northern blotting analyses showed that the BoVapC1 toxin had a ribonuclease activity on the initiator tRNA
, implying that degradation of tRNA
might trigger growth arrest in
Furthermore, the BoVapBC1 system was found to contribute to survival against prolonged exposure at 4°C. This is the first study to identify the function of TA systems in cold adaptation.