Involvement of Tn4430 in transfer of Bacillus anthracis plasmids mediated by Bacillus thuringiensis plasmid pXO12

Abstract

The self-transmissible plasmid pXO12 (112.5 kilobases [kbj), originally isolated from strain 4042A of BaciUus thuringiensis subsp. thuringiensis, codes for production of the insecticidal crystal protein (Cry'). The mechanism of pXO12-mediated plasmid transfer was investigated by monitoring the cotransfer of the tetracycline resistance plasmid pBC16 (4.2 kb) and the Bacillus anthracis toxin and capsule plasmids, pXOl (168 kb) and pXO2 (85.6 kb), respectively. In matings of B. anthracis donors with B. anthracis and Bacillus cereus recipients, the number of Tcr transcipients ranged from 4.8 x 104 to 3.9 x 106/ml (frequencies ranged from 1.6 x 10-4 to 7.1 x 10-2), and 0.3 to 0.4% of them simultaneously inherited pXO1 or pXO2. Physical analysis of the transferred plasmids suggested that pBC16 was transferred by the process of donation and that the large B. anthracis plasmids were transferred by the process of conduction. The transfer of pXO1 and pXO2 involved the transposition of Tn4430 from pXO12 onto these plasmids. DNA-DNA hybridization experiments demonstrated that Tn4430 was located on a 16.0-kb AvaI fragment of pXO12. Examination of Tra-and Cryderivatives of pXO12 showed that this fragment also harbored information involved in crystal formation and was adjacent to a restriction fragment containing DNA sequences carrying information required for conjugal transfer.Recent reports from our laboratory have concerned the identification and characterization of six self-transmissible plasmids from five subspecies of Bacillus thuringiensis (1,19). One of these plasmids, designated pXO12 (112.5 kilobases [kb]), was isolated from strain 4042A of B. thuringiensis subsp. thuringiensis. Plasmid pXO12 is capable of mediating its own transfer as well as that of a large range of Bacillus plasmids among strains of Bacillus anthracis, Bacillus cereus, and B. thuringiensis. In addition to conjugal transfer functions, pXO12 also encodes production of the insecticidal toxin known as the 8-endotoxin or the parasporal crystal (Cry').The widespread occurrence of large self-transmissible plasmids among B. thuringiensis strains suggests that conjugation may be an important means of plasmid dissemination in naturally occurring Bacillus populations (4). In the laboratory, this mating system has provided us with an efficient method of shuttling a wide range of plasmids among B. thuringiensis, B. cereus and B. anthracis. For example, the utility of this conjugation system in the genetic analysis of the B. anthracis toxin and capsule plasmids, pXO1 and pXO2, respectively, has been well documented (1,6,19,24).Prior to the development of this mating system, the most reliable system available for transferring plasmids among these three Bacillus species was transduction (21). Therefore, the importance of this system as an additional means of genetic exchange among these organisms warrants further genetic and physical analysis of these conjugative plasmids. We have been interested in determining the mechanism of pXO12-mediated transfer of both lar...

Key role of poly-γ-dl-glutamic acid in immune evasion and virulence of Staphylococcus epidermidis

“…The genetic information for PGA production in B. anthracis is located on a plasmid (pXO2) (19,20) and shows high genetic mobility (21). It might have been transferred between B. anthracis and staphylococci and from one strain of Staphylococcus to another.…”

Glycine-induced cryotransformation of plasmids into Bacillus anthracis

“…Thorne's group showed the conjugative-like mobilization of large (pX0 1 and pX02) and small (pBC16) plasmids mediated by B. thuringiensis fertility plasmids of the Cry+ family (Thorne, 1985;Battisti et al, 1985;Reddy et al, 1987). The involvement of Tn4430, located on one of these plasmids, pX012, in mobilization of pXOl and pX02 was demonstrated (Green et al, 1989). This group also used the cryptic plasmid pLS20 to transfer the small cloning vector plasmids pBC16 and PUB1 10 among a wide variety of Bacillus species including B. subtilis and B. anthracis (Koehler & Thorne, 1987).…”

A Novel FtsZ-Like Protein Is Involved in Replication of the Anthrax Toxin-Encoding pXO1 Plasmid inBacillus anthracis

“…This plasmid also contains genes that are involved in germination of the spores and genes such as atxA and pagR that regulate the expression of the anthrax toxin and other virulence factors (3,10,19,28). Plasmid pXO1 also contains a number of genes resembling those involved in the horizontal transfer of plasmids (9,19,28), suggesting that this plasmid may mediate its own transfer to other related organisms.Very little is known about the replication properties of the pXO1 plasmid. Studies of the identification of the pXO1 replicon have been hampered since this plasmid does not encode proteins that share significant similarity with known replication initiator proteins encoded by other plasmids (5, 6, 17) (http://www.essex .ac.uk/bs/staff/osborn/DPR_home.htm).…”