Transformation of Escherichia coli JM109 using pUC19 by the Yoshida effect

Nano-delivery platforms for bacterial gene transformation: suitability and challenges

Nano-scale particles (NPs) have gained increased interest as non-viral vectors for nucleic acid delivery due to their ability to penetrate through unabraded cell membranes. The previous studies performed have evaluated the nanomaterials for their microbial transformation proficiency but have not compared the relative efficacy. The present study aims to identify the most proficient nano-delivery vehicle among the chemically synthesized/functionalized non-metal oxide, metal/metal oxide, and carbon-based (carbon nanotube (CNT), graphene oxide (GO)) nanomaterial(s) (NMs) for the transformation of two gram-negative bacteria, i.e., Escherichia coli and Agrobacterium tumefaciens. The microscopy and spectroscopy studies helped to identify the interaction, adhesion patterns, transformation efficiencies, better delivery, and expression of the target gfp gene by use of NMs. Loading of pgfp on all NMs imparted protection to DNAse I attack except ZnO NPs with maximum by chitosan, layered double hydroxide (LDH), and GO NM-plasmid DNA conjugates. The CNTs and GO significantly enhanced the extra- and intra-cellular protein content, respectively, in both bacteria. However, GO and CNT significantly decreased the cell viability in a time-dependent manner while AuNPs exhibited negligible cell toxicity. Therefore, this study identified the comparative efficiency of metal/metal oxide, non-metal oxide, and carbon nanomaterials with AuNPs as the most biosafe while LDH and chitosan NPs being the most proficient alternative tools for the genetic transformation of gram-negative bacteria by simple incubation method.

CSU52, a novel regulator functions as a repressor of L-sorbose utilization in Candida albicans

Background and Objectives

Monosomy of chromosome 5 associated with utilization of non-canonical sugar L-sorbose is one of the well-studied aneuploidies in Candida albicans. Stress-induced ploidy changes are crucial determinants for pathogenicity and genetic diversity in C. albicans. The five scattered regulatory regions (A, B, C, 135, and 139) comprising of two functionally redundant pathways (SUR1 and SUR2) were found to be responsible for the growth on L-sorbose. So far, three genes such as CSU51, CSU53 and CSU57 have been identified in region A, region 135 and region C, respectively. In this study we have verified the role of region B in this regulatory pathway.

Materials and Methods

We employed a combinatorial gene deletion approach to verify the role of region B followed by co-over expression studies and qRT-PCR to identify the regulatory role of this region.

Results

We confirmed the role of region B in the regulation of SOU1 gene expression. The qRT-PCR results showed that regulation occurs at transcriptional level along with other two regions in SUR1 pathway. A previously uncharacterized open reading frame in region B has been implicated in this regulation and designated as CSU52. Integrating multiple copies of CSU52 in the genome at tandem, suppresses the growth of recipient strain on L-sorbose, establishing it as a repressor of SOU1 gene.

Conclusion

This finding completes the identification of regulators in SUR1 pathway. This result paves the way to study the underlying molecular mechanisms of SOU1 gene regulation that in-turn helps to understand stress induced aneuploidy.

Artificial transformation methodologies for improving the efficiency of plasmid DNA transformation and simplifying its use

The uptake of exogenous DNA materials through the cell membrane by bacteria, known as transformation, is essential for the genetic manipulation of bacteria and, thus, plays key roles in biotechnological and biological research. The efficiency of natural transformation is very low; therefore, various artificial transformation methods have been developed for simple and efficient bacterial transformation. The basic bacterial transformation method is based on chemical, physical, and electrical processes and other means to permeabilize the bacterial cell membrane to allow plasmid DNA uptake. With the introduction of novel chemicals, materials, and devices and the optimization of protocols, new transformation methods have become simpler, cheaper, and more reproducible for use in diverse bacterial species compared with conventional methods. In this review, artificial transformation methods have been classified according to the membrane-permeabilizing mechanisms employed by them. Their influential factors, transformation efficiency, advantages, disadvantages, and practical applications are briefly illustrated. Finally, physicochemical transformation as a new bacterial transformation technique has also been described.

Clay-induced DNA breaks as a path for genetic diversity, antibiotic resistance, and asbestos carcinogenesis

Natural clays and synthetic nanofibres can have a severe impact on human health. After several decades of research, the molecular mechanism of how asbestos induces cancer is not well understood. Different fibres, including asbestos, can penetrate cell membranes and introduce foreign DNA in bacterial and eukaryotic cells. Incubating Escherichia coli under friction forces with sepiolite, a clayey material, or with asbestos, causes double-strand DNA breaks. Antibiotics and clays are used together in animal husbandry, the mutagenic effect of these fibres could be a pathway to antibiotic resistance due to the friction provided by peristalsis of the gut from farm animals in addition to horizontal gene transfer. Moreover, we raise the possibility that the same mechanism could generate bacteria diversity in natural scenarios, playing a role in the evolution of species. Finally, we provide a new model on how asbestos may promote mutagenesis and cancer based on the observed mechanical genotoxicity.