Comparison of base substitutions in response to nitrogen ion implantation and 60Co-gamma ray irradiation in Escherichia coli

Xie, Chenbo; Xu, An; Wu, Lijun; Yao, Jianmin; Yang, Jian‐Bo; Zhang, Yu

doi:10.1590/s1415-47572004000200025

Cited by 14 publications

(3 citation statements)

References 20 publications

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“…GC-to-AT and AT-to-GC transitions were detected in high numbers, agreeing with mutational patterns detected in previously evolved IR-resistant E. coli populations (45,46). Base substitutions are approximately 50% transitions and 50% transversions, whereas E. coli exposed to 60 Co gamma ray irradiation exhibit transversions at about four times the frequency of transitions (45,55). In particular, GC-to-TA transitions appeared at very high levels in each population, indicative of significant templatestrand 8-oxodG-mediated mutagenesis (56).…”

Section: Figsupporting

confidence: 86%

“…While enhanced DNA repair is a hallmark of the previously evolved populations and the populations presented here, it appears as though the enhancements are indeed different. In addition, the frequency of transversion mutations detected in the new populations (ϳ50% of all mutations) is far higher than that observed in the earlier studies (ϳ20% of all mutations) (45,55). This appears to be due to the extreme amount of detected GC-to-TA transitions, specifically.…”

Section: Direct Competition Between Two Pathways To Ir Resistance Dictates Adaptationcontrasting

confidence: 64%

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Experimental Evolution of Extreme Resistance to Ionizing Radiation in Escherichia coli after 50 Cycles of Selection

et al. 2019

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In previous work (D. R. Harris et al., J Bacteriol 191:5240–5252, 2009, https://doi.org/10.1128/JB.00502-09; B. T. Byrne et al., Elife 3:e01322, 2014, https://doi.org/10.7554/eLife.01322), we demonstrated that Escherichia coli could acquire substantial levels of resistance to ionizing radiation (IR) via directed evolution. Major phenotypic contributions involved adaptation of organic systems for DNA repair. We have now undertaken an extended effort to generate E. coli populations that are as resistant to IR as Deinococcus radiodurans. After an initial 50 cycles of selection using high-energy electron beam IR, four replicate populations exhibit major increases in IR resistance but have not yet reached IR resistance equivalent to D. radiodurans. Regular deep sequencing reveals complex evolutionary patterns with abundant clonal interference. Prominent IR resistance mechanisms involve novel adaptations to DNA repair systems and alterations in RNA polymerase. Adaptation is highly specialized to resist IR exposure, since isolates from the evolved populations exhibit highly variable patterns of resistance to other forms of DNA damage. Sequenced isolates from the populations possess between 184 and 280 mutations. IR resistance in one isolate, IR9-50-1, is derived largely from four novel mutations affecting DNA and RNA metabolism: RecD A90E, RecN K429Q, and RpoB S72N/RpoC K1172I. Additional mechanisms of IR resistance are evident. IMPORTANCE Some bacterial species exhibit astonishing resistance to ionizing radiation, with Deinococcus radiodurans being the archetype. As natural IR sources rarely exceed mGy levels, the capacity of Deinococcus to survive 5,000 Gy has been attributed to desiccation resistance. To understand the molecular basis of true extreme IR resistance, we are using experimental evolution to generate strains of Escherichia coli with IR resistance levels comparable to Deinococcus. Experimental evolution has previously generated moderate radioresistance for multiple bacterial species. However, these efforts could not take advantage of modern genomic sequencing technologies. In this report, we examine four replicate bacterial populations after 50 selection cycles. Genomic sequencing allows us to follow the genesis of mutations in populations throughout selection. Novel mutations affecting genes encoding DNA repair proteins and RNA polymerase enhance radioresistance. However, more contributors are apparent.

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Section: Figsupporting

confidence: 86%

Section: Direct Competition Between Two Pathways To Ir Resistance Dictates Adaptationcontrasting

confidence: 64%

Experimental Evolution of Extreme Resistance to Ionizing Radiation in Escherichia coli after 50 Cycles of Selection

et al. 2019

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“…Hitherto, no chemical agent is known to be capable of inducing AT to CG transversions (Baltz 2001 ). AT to CG transversions, on the other hand, were discovered in cells exposed to gamma radiation (Xie et al 2004 ). One type of ionizing radiation, gamma rays are thought to be the most energetic radiations.…”

Section: Discussionmentioning

confidence: 99%

Statistical optimization and gamma irradiation on cephalosporin C production by Acremonium chrysogenum W42-I

Ibrahim,

El-Housseiny,

Aboshanab

et al. 2023

AMB Expr

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Most antibiotics now used in clinical practice are cephalosporins. Acremonium (A.) chrysogenum W42-I is an intermediate strain out of W42 strain improvement program whose productivity is above that of the wild-type strain to produce the broad-spectrum antibacterial cephalosporin C (CPC). As a result, fermentation process optimization is considered because it offers the ideal environment for strains to reach their full potential. Our research aimed to combine a rational design to regulate the fermentation process environment and culture media as well as to develop mutants with high productivity. Different media were tested to obtain maximum CPC production. To maximize the production of CPC, some environmental parameters were experimentally optimized via the Box-Behnken design used for response surface methodology (RSM). There were 17 tests conducted, and each experiment's reaction was recorded. Improvement of the CPC production was further achieved via mutagenesis using gamma radiation. Results revealed that a pH of 4, an incubation period of 4 days, and an inoculum size of 1% v/v using the optimized media (CPC2) were the optimum conditions for enhancing the CPC production by 4.43-fold. In addition, gamma irradiation further enhanced production to reach 3.46-fold using an optimum dose of 2 KGy. In conclusion, in comparison to initial production levels, CPC production increased 4.43-fold because of nutritional and environmental optimization. The mutant AC8 demonstrated a roughly 3.46-fold increase in activity against its parent type. Moreover, subsequent AC8 mutant culture demonstrated excellent genetic stability.

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Enhancement of epoxide hydrolase production by ⁶⁰Co gamma and UV irradiation mutagenesis of Aspergillus niger ZJB‐09103

Jin

Ouyang

2016

Biotech and App Biochem

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An effective epoxide hydrolase (EH) production strain was mutagenized using Co gamma and UV irradiation. Among positive mutant strains, the EH activity of C2-44 reached 33.7 U/g, which was 267% as much as that of the original Aspergillus niger ZJB-09103. Compared with the wild type, there were significant changes in morphology for C2-44, including the color of mycelia on the slants and the shape of conidial head. In addition, glucose and soybean cake were the optimal carbon and nitrogen source in terms of EH activity for the mutant C2-44 instead of soluble starch and peptone for the wild-type strain. The reaction time required to reach 99% enantiomeric excesses of (S)-epichlorohydrin from racemic substrate was shortened significantly by the mutant C2-44. This phenomenon was probably explained by the higher V for hydrolysis of racemic epichlorohydrin by C2-44 compared with Aspergillus niger ZJB-09103.

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Comparison of base substitutions in response to nitrogen ion implantation and 60Co-gamma ray irradiation in Escherichia coli

Cited by 14 publications

References 20 publications

Experimental Evolution of Extreme Resistance to Ionizing Radiation in Escherichia coli after 50 Cycles of Selection

Experimental Evolution of Extreme Resistance to Ionizing Radiation in Escherichia coli after 50 Cycles of Selection

Statistical optimization and gamma irradiation on cephalosporin C production by Acremonium chrysogenum W42-I

Enhancement of epoxide hydrolase production by ⁶⁰Co gamma and UV irradiation mutagenesis of Aspergillus niger ZJB‐09103

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Comparison of base substitutions in response to nitrogen ion implantation and 60Co-gamma ray irradiation in Escherichia coli

Cited by 14 publications

References 20 publications

Experimental Evolution of Extreme Resistance to Ionizing Radiation in Escherichia coli after 50 Cycles of Selection

Experimental Evolution of Extreme Resistance to Ionizing Radiation in Escherichia coli after 50 Cycles of Selection

Statistical optimization and gamma irradiation on cephalosporin C production by Acremonium chrysogenum W42-I

Enhancement of epoxide hydrolase production by 60Co gamma and UV irradiation mutagenesis of Aspergillus niger ZJB‐09103

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Enhancement of epoxide hydrolase production by ⁶⁰Co gamma and UV irradiation mutagenesis of Aspergillus niger ZJB‐09103