Temperature-dependent expression of different guanine-plus-cytosine content 16S rRNA genes in Haloarcula strains of the class Halobacteria

Abstract

Haloarcula strains, which are halophilic archaea, harbour two to three copies of 16S rRNA genes (rrsA, rrsB and rrsC) in their genomes. While rrsB and rrsC (rrsBC) show almost identical sequences, rrsA shows 4-6% sequence difference and 1-3% guanine-plus-cytosine content (P GC ) difference compared to rrsBC. Based on the strong correlation between the P GC of 16S rRNA genes and the growth temperatures of the prokaryotes, we hypothesised that high-P GC rrsA and low-P GC rrsBC are expressed at high and low temperatures, respectively. To verify the hypothesis, we performed sequence analyses and expression surveys of each 16S rRNA gene in eight Haloarcula strains. The secondary structure prediction of the 16S rRNA via computer simulation showed that the structural stability of 16S rRNAs transcribed from rrsA was higher than that of 16S rRNAs transcribed from rrsBC. We measured expression levels of rrsA and rrsBC under various temperature conditions by reverse-transcriptase quantitative PCR. The expression ratio of high-P GC rrsA to low-P GC rrsBC increased with cultivation temperatures in seven of eight Haloarcula strains. Our results suggest that the transcription of high-P GC rrsA and low-P GC rrsBC may be regulated in response to environmental temperature, and that 16S rRNAs transcribed from high-P GC rrsA function under high temperature conditions close to the maximum growth temperature.

Occurrence of randomly recombined functional 16S rRNA genes in Thermus thermophilus suggests genetic interoperability and promiscuity of bacterial 16S rRNAs

“…ruber , and 44.0% for D . radiodurans , respectively, whereas that of the consensus nucleotides was 59.5% (Supplementary Table S2); these tendencies were in agreement with the general rule of temperature adaptation of 16S rRNAs 22,23 . Despite the marked difference in the evolutionary pattern of each individual 16S rRNA, the “cold-adapted” D .…”

Ubiquitousness of Haloferax and Carotenoid Producing Genes in Arabian Sea Coastal Biosystems of India

“…The red pigments were also haloarchaea members ( Haloferax genus) resistant to saturated NaCl (6M). Previous studies have shown that G + C content is associated with genome stability in high saline and abiotic stress [ 55 , 56 , 57 , 58 ]. Thus, it is established that high G + C content in haloarchaeal serves as a protective measure from environmental stress, prevention of thymidine dimers and reduces UV-induced mutations [ 20 , 57 ].…”