Mutagenic Consequences Of Chemical Reaction with DNA
Philip L. Grover in Chemical Carcinogens and DNA, 2019
If insertion occurs into a gene, the gene may be inactivated. Translocating elements include the mutator bacteriophage Mu, insertion sequences, identifiable only by their inactivating effect, and transposons which carry identifiable genes. Many plasmid drug resistance genes are on transposons so that not only may resistance to a drug be transferred between bacteria on a plasmid, but it may be transferred between plasmids as part of a transposon. This natural genetic engineering is of considerable medical importance, and the mechanism is under active investigation. It does not seem related to conventional recombination. As well as the role of transposons in drug resistance, insertion sequences may be involved in such phenomena as bacterial conjugation and the unstable maize mutation systems examined in the classic studies of McClintock.24
Joshua Lederberg (1925–2008)
Krishna Dronamraju in A Century of Geneticists, 2018
Josh received the Eli Lilly Award as the outstanding young bacteriologist, presented at the Society of American Bacteriologists annual meeting in 1953. Concurrently, there was a swirl of controversy about the process of bacterial conjugation. The Lederbergs, in cooperation with their longtime friend, Italian geneticist Luigi (Luca) Cavalli-Sforza from Milan, found that the asymmetry in bacterial recombination was controlled by a fertility factor on the cell surface that was readily transmissible.
Physiology and Growth
Paul Pumpens in Single-Stranded RNA Phages, 2020
Historically, the penetration process was explained by functioning of pili: (i) like a hollow tube for the nucleic acid transport (Brinton 1965); (ii) as two parallel protein filaments (Brinton 1971), (iii) by retracting into the cell after receiving an appropriate stimulus and sequential depolymerization of pili subunits, which resulted in RNA phage being pulled to the base of the pilus, where it injected its RNA (Curtiss 1969; Marvin and Hohn 1969). The latter mechanism was supported by Bradley (1972c), who found by electron microscopy studies that the infection of P. aeruginosa with the phage PP7 resulted in an average reduction in pilus length of about 50%, and that phage particles were almost always at the bases of the pili. Experiments similar to the above were carried out by Paranchych et al. (1971) with the phage R17 and F-piliated E. coli. These studies also showed that the interaction of pili with the RNA phage resulted in an overall shortening of the pilus lengths. However, the shortening of F pili was accompanied by a corresponding increase of cell-free F pilus fragments in the medium, suggesting that the phage interaction with the F pili had resulted in a fragmentation of the F pili rather than retraction. The foregoing observations were also interpretable, however, in terms of retraction of old F pili followed by the outgrowth and release of newly synthesized F pili (Paranchych 1975). Reduction of F pili was observed also by infection with filamentous DNA phages f1 (Jacobson 1972) and M13 (O'Callaghan et al. 1973b). Nevertheless, Ou and Anderson (1970) demonstrated strong evidence against the retraction model by studies where cells were involved in bacterial conjugation and the exchange of genetic information occurred between pairs of cells which were never visibly in close contact, suggesting that the donor DNA is transferred to the recipient via the F pilus in the absence of the F pilus retraction (for qualified discussion see Paranchych 1975).
Non-antibiotic antibacterial peptides and proteins of Escherichia coli: efficacy and potency of bacteriocins
Published in Expert Review of Anti-infective Therapy, 2021
Juraj Bosák, Matěj Hrala, Lenka Micenková, David Šmajs
Another group of colicins with broad activities against E. coli are colicins U, Y, and R, which share a close sequence similarity (~90%) and evolutionary relationship [70,152,153]. They are encoded on small plasmids with a limited prevalence (<1%) among E. coli isolates [96]. Colicins U, Y, and R recognize outer membrane protein A (OmpA) as a receptor on susceptible bacteria. OmpA is a transmembrane β-barrel protein that belongs to major surface proteins of E. coli and plays an important role in biofilm formation, bacterial conjugation, host cell adhesion and invasion, formation of transporting pores, and multidrug resistance (reviewed in [154]). All three colicins share an almost identical spectrum of activity against Escherichia and, for example, colicins U and Y inhibited most of E. coli isolates including all tested multidrug-resistant O25b-ST131 isolates [150]. Colicins U and Y have been shown to bind to amino acid residues in extracellular loop 1 [150], a loop that is evolutionary conserved and necessary for bacterial virulence; for example it plays an important role in virulence of meningitis-associated E. coli [155–157].
Yersinia pseudotuberculosis YopE prevents uptake by M cells and instigates M cell extrusion in human ileal enteroid-derived monolayers
Published in Gut Microbes, 2021
Alyssa C. Fasciano, Gaya S. Dasanayake, Mary K. Estes, Nicholas C. Zachos, David T. Breault, Ralph R. Isberg, Shumin Tan, Joan Mecsas
Yptb YPIII strains used for this work are listed in Table S5. The following strains were generated using bacterial conjugation described in.52 To generate ΔyopH and ΔyopO, pCVD442-yopHKO or pCVD442-yopOKO were conjugated into WT YPIII (JM301), respectively. To generate ΔyopEH and ΔyopEO, pCVD442-yopHKO or pCVD442-yopOKO were conjugated into ΔyopE YPIII (WS125c), respectively. Plasmids are described in.39 To generate ΔyadA and Δinv, pCVD442-yadAKO or pCVD442-invKO was conjugated into WT YPIII (JM301), respectively. To generate Δinv/yadA, pCVD442-yadAKO was conjugated into Δinv (ERG9). Plasmids are described in.53
Related Knowledge Centers
- Antimicrobial Resistance
- Bacteria
- Horizontal Gene Transfer
- Pilus
- Sexual Reproduction
- Transduction
- Transposable Element
- Transformation
- Mating
- Plasmid