Frequent Transposition of Multiple Insertion Sequences in Geobacillus kaustophilus HTA426

Abstract

Geobacillus kaustophilus HTA426 is a thermophilic bacterium whose genome harbors numerous insertion sequences (IS). This study was initially conducted to generate mutant genes for thermostable T7 RNA polymerase in G. kaustophilus; however, relevant experiments unexpectedly identified that the organism transposed multiple IS elements and produced derivative cells that expressed a silent gene via transposition. The transposed elements were diverse and included members of the IS4, IS701, IS1634, and ISLre2 families. The transposition was relatively active at elevated temperatures and generated 4–9 bp of direct repeats at insertion sites. Transposition was more frequent in proliferative cells than in stationary cells but was comparable between both cells when sigX, which encodes an extra-cytoplasmic function sigma factor, was forcibly expressed. Southern blot analysis indicated that IS transposition occurred under growth inhibitory conditions by diverse stressors; however, IS transposition was not detected in cells that were cultured under growth non-inhibitory conditions. These observations suggest that G. kaustophilus enhances IS transposition via sigX-dependent stress responses when proliferative cells were prevented from active propagation. Considering Geobacillus spp. are highly adaptive bacteria that are remarkably distributed in diverse niches, it is possible that these organisms employ IS transposition for environmental adaptation via genetic diversification. Thus, this study provides new insights into adaptation strategies of Geobacillus spp. along with implications for strong codependence between mobile genetic elements and highly adaptive bacteria for stable persistence and evolutionary diversification, respectively. This is also the first report to reveal active IS elements at elevated temperatures in thermophiles and to suggest a sigma factor that governs IS transposition.

Influence of Redox Imbalances on the Transposition of Insertion Sequences in Deinococcus geothermalis

“…In addition to the transposition of IS4, IS5, IS630, and IS200/IS605 into thyA through gamma-irradiation in D. radiodurans [49], another study recently reported that heat stress enhanced the transposition of multiple ISs via sigX-dependent stress response in Geobacillus kaustophilus [55]. In this case, the IS4, IS701, IS1634, and ISLre2 family members were transposed.…”

Hydrogen peroxide treatment induces the transposition of an insertion sequence in Deinococcus radiopugnans DY59

“…Insertion sequence transposition has been detected under various environmental stressors, such as nutrient deprivation, temperature changes, metal ion exposure, and oxidative stress caused by UV irradiation, gamma irradiation, and H 2 O 2 treatment (Ohtsubo et al, 2005;Twiss et al, 2005;Kharat et al, 2006;Mijnendonckx et al, 2011;Suzuki et al, 2021). Interestingly, this active transposition of IS elements was found to vary in a species-specific manner.…”

Whole-genome sequence of Geobacillus thermodenitrificans K1041, a genetically tractable strain representative of the genus Geobacillus

“…The cells were cultured at 60°C using lysogeny broth under aerobic conditions. Genomic DNA was extracted from the cells using a cetyltrimethylammonium bromide-based method ( 3 ) and solubilized in 1 mL of a buffer that contained Tris-HCl at pH 8.0 (10 mM) and EDTA (1 mM). Genomic DNA was then purified from an aliquot of the resulting solution using NucleoSpin gDNA Clean-up kit (Takara Bio, Otsu, Japan).…”