EC Microbiology

There are two kinds of genetic transformation as described in the books of molecular genetics of bacteria: natural transformation and artificial transformation. Many of us are familiar only with artificial transformation because of in-vitro gene cloning experiments with recombinant DNA in gram-negative E. coli K-12. This is formed by joining a DNA fragment of choice to a multicopy cloning vector pBR322 and its entry into the gram-negative E. coli K-12, made competent by its growth in rich broth containing calcium chloride and thermal shock. In natural transformation as studied with gram-positive pathogen S. pneumoniae, several investigators have reported the entry of exogenous linear DNA fragments (eclipse phase) but how does such linear DNA fragments originate? However, the established investigators are still not considering our concept of genes, operons and regulons. They have used the word fratricide without the knowledge of growth curve. Now with the knowledge we want to think this pathogen grows in clusters but prevail in chains. Our work on genetic transformation has established that the gram-positive pathogenic bacterium S. pneumoniae grows in three phases-pre-competent, competent and post-competent (spheroplast) without the requirement of any exogenous linear DNA fragments.

Keywords: Genetic Transformation; Spheroplast; E. coli K-12; S. pneumoniae; Natural Transformation; Artificial Transformation; DNA Fragments; pBR322

1. Griffith F. “The significance of pneumococcal types”. The Journal of Hygiene 27 (1928): 113-159.
2. Avery OT., et al. “Studies on the chemical nature of the substance inducing transformation of pneumococcal types”. Journal of Experimental Medicine 89 (1944): 137-158.
3. Palchaudhuri S., et al. “Characterization by electron microscopy of fused F- prime factors in coli”. Proceedings of the National Academy of Sciences of the United States of America 69 (1972): 873-876.
4. Watson JD and Crick FHC. “Molecular structure of nucleic acids: a structure for deoxyribose nucleic acid”. Nature 171 (1953): 737-738.
5. , et al. “Construction of biologically functional bacterial plasmids In vitro”. Proceedings of the National Academy of Sciences of the United States of America 70 (1973): 3240.
6. Morrison DA. “Transformation in pneumococcus: existence and properties of a complex involving donor deoxyribonucleate single strands in eclipse”. Journal of Bacteriology 132 (1977): 576-583.
7. Lacks SA. In The Pneumococcus-edited by EI Tuomanen, T J Mitchell, D A Morrison, B G Spratt. 2004-ASM Press-Washington DC (2004).
8. Palchaudhuri S. “Growth curve of pneumoniae-a serious pathogen”. Journal of Medical Case Reports 1 (2021): 1-3.
9. Morrison DA., et al. “Isolation and characterization of three new classes of transformation-deficient mutant of Streptococcus pneumoniae that are defective in DNA transport and genetic recombination”. Journal of Bacteriology 156 (1983): 281-290.
10. Haverstein LS and Ola Johnsborg. “New insights into the pneumococcal fratricide: relationship to clumping and identification of a novel immunity factor”. Molecular Microbiology4 (2006): 1297-1307.
11. Palchaudhuri S and Chakraborty S. “Xylitol in human medicine when antibiotic resistance crisis arises (Ms in preparation)” (2023).