EDEMA FACTOR AND PHOSPHOLIPASE RELEASE BY A STRAIN OF BACILLUS CEREUS

Phages preying on Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis: past, present and future

Many bacteriophages (phages) have been widely studied due to their major role in virulence evolution of bacterial pathogens. However, less attention has been paid to phages preying on bacteria from the Bacillus cereus group and their contribution to the bacterial genetic pool has been disregarded. Therefore, this review brings together the main information for the B. cereus group phages, from their discovery to their modern biotechnological applications. A special focus is given to phages infecting Bacillus anthracis, B. cereus and Bacillus thuringiensis. These phages belong to the Myoviridae, Siphoviridae, Podoviridae and Tectiviridae families. For the sake of clarity, several phage categories have been made according to significant characteristics such as lifestyles and lysogenic states. The main categories comprise the transducing phages, phages with a chromosomal or plasmidial prophage state, γ-like phages and jumbo-phages. The current genomic characterization of some of these phages is also addressed throughout this work and some promising applications are discussed here.

Production of bacteriophage by temperature-sensitive sporulation mutants of Bacillus cereus T

Five temperature-sensitive sporulation mutants of Bacillus cereus T have been isolated. These mutants are blocked at stage 0 of sporulation at the restrictive temperature (37 C) but are able to sporulate at nearly normal frequencies at the permissive temperature (26 C). A bacteriophage that forms a stable lysogen in the parent strain is induced at increased frequencies in the mutants. This induction is accompanied, in some of the mutants, by a reduction in immunity to the phage. Revertants, selected for their ability to sporulate normally at both temperatures, lose their ability to produce high titers of the phage. In addition to this lytic phage, an apparently defective phage has been found in lysates of the mutants. Strains cured of the plaque-forming phage still carry the defective phage. Comparisons of physical and biological properties of the plaque-forming phage with those of the two Bacillus cereus phages most similar to it have shown that this phage is not identical to either of them. The maximal titer of phage produced in cultures of the parent strain is about 10(3) plaque-forming units (PFU) per ml at both temperatures. The maximal titers of phage produced by the mutant are 4 x 10(9) PFU/ml at 37 C and 7 x 10(8) PFU/ml at 26 C. Both mutant and parent strains release over 90% of the phage they produce after the onset of stationary phase.

Comparison of Bacillus cereus bacteriophages CP-51 and CP-53

Transducing bacteriophages CP-51 and CP-53 were compared. Unlike CP-51, CP-53 appeared to be a lysogenizing phage. CP-51 gave greater frequencies of co-transduction for linked markers than did CP-53. CP-51 was found to be a larger phage which carried more deoxyribonucleic acid (DNA) than CP-53. CP-51 DNA contained about 43% guanine plus cytosine and in addition contained 5-hydroxymethyluracil in place of thymine. CP-53 DNA contained no unusual bases; its guanine plus cytosine content was 37%.

Transduction in Bacillus cereus by each of two bacteriophages

The ability of phage CP-51 to mediate transduction both homologously and heterologously in some of its hosts was investigated. CP-51 was shown to transduce Bacillus cereus strains 6464, 9139, and T in addition to 569 which was reported earlier from this laboratory. Furthermore, CP-51 grown on B. thuringiensis was shown to transduce some mutants of B. cereus. During this investigation, a second transducing phage for B. cereus 569 was isolated from lysates of phage CP-51 grown on B. cereus 6464. This phage, designated CP-53, is carried by wild-type strain 6464 possibly as prophage. All auxotrophic mutants of B. cereus 569 tested, those requiring tryptophan, histidine, methionine, and leucine, were transduced to prototrophy by CP-53. Electron micrographs of the two phages revealed that CP-51 has a tail core surrounded by a contractile sheath and CP-53 has a long flexible tail without a contractile sheath. CP-53 is stable in the cold, whereas CP-51 is rapidly inactivated at 4 C.

Inducible lysis clostridium tetani

Lysis was induced in seven strains of Clostridium tetani by exposure to mitomycin C. The search for a suitable indicator strain to detect bacteriophage in lysates has, so far, been unsuccessful. Inhibition studies on macromolecular synthesis during induction have shown that deoxyribonucleic acid, ribonucleic acid, and protein syntheses are all involved in the lysis induced by mitomycin C. In experiments comparing toxin and protein content in induced and uninduced cells of C. tetani, the toxin-protein ratio proved to be the same in both systems up to the point of lysis. Several possible hypotheses deduced from these results are discussed.