Similar mutation rates but different mutation spectra in moderate and extremely halophilic archaea.

Archaea are a major part of Earth's microbiota and extremely diverse. Yet, we know very little about the process of mutation that drives such diversification. To expand beyond previous work with the moderate halophilic archaeal species Haloferax volcanii, we performed a mutation-accumulation experiment followed by whole-genome sequencing in the extremely halophilic archaeon Halobacterium salinarum.

Streptomycin and nalidixic acid elevate the spontaneous genome-wide mutation rate in Escherichia coli.

Since antibiotic resistance is a growing public health problem worldwide, it is important to understand how antibiotics and spontaneous mutations cooperate and shape the genome-wide mutation rate and spectrum. Here, we quantitatively evaluate genome-wide mutational profiles of Escherichia coli after long-term subinhibitory exposure to a broad-spectrum (streptomycin) and a narrow-spectrum antibiotic (nalidixic acid), using a mutation accumulation design combined with whole-genome resequencing of replicate lines as a mutagenicity test. We determined that, while the genome-wide mutation rate is slightly higher in the streptomycin-treated lines compared to the control lines, there is a significant increase in the nalidixic acid-treated lines.