Random mutagenesis of a Pseudomonas putida strain capable of acclimating to high-concentration formaldehyde via atmospheric and room temperature plasma(ARTP)

Abstract

Formaldehyde has strong cytotoxicity to organisms and may cause nasopharyngeal cancer and probably leukemia. This study is intended to investigate a highly formaldehyde-resistant utilizer, the Pseudomonas putida W1 strain. Bacterial strain W1 isolated from untreated activated sludge samples collected from heavily formaldehyde- and aniline-contaminated areas was identified using morphological characteristics and molecular techniques. The formaldehyde concentration in the medium decreased with the growth of strain W1. The degradation of formaldehyde concentration depends on the cell number of strain W1. The W1 strain completely consumed 0.5 g L-1 of nearly 98% formaldehyde within 48 h. Atmospheric and room temperature plasma (ARTP) was applied to improve the tolerance to formaldehyde and the genetic stability of P. putida. The protocol for rapid mutation was established by different intervals with a fatality rate reaching 99% and then compared with the dual gradient plate screening method. Growth of the isolated mutant WMZ120-5 strain on formaldehyde was possible up to at least 3 g L-1, and survival at up to a concentration of 20 g L-1 was possible after stepwise acclimatization. At such high concentrations of formaldehyde, the mutant WMZ120-5 exhibited approximately seven-fold higher expression than the original strain W1. The characteristics of the mutant after mutagenesis showed good genetic stability after the 10th subculture. Our study demonstrated that strain WMZ120-5 has great potential to utilize formaldehyde at high concentrations in the environment.