UNIQUE REGULATION OF CRYSTAL PROTEIN PRODUCTION IN BACILLUS-THURINGIENSIS SUBSP YUNNANENSIS IS MEDIATED BY THE CRY PROTEIN-ENCODING 103-MEGADALTON PLASMID
G. Srinivas et al., UNIQUE REGULATION OF CRYSTAL PROTEIN PRODUCTION IN BACILLUS-THURINGIENSIS SUBSP YUNNANENSIS IS MEDIATED BY THE CRY PROTEIN-ENCODING 103-MEGADALTON PLASMID, Applied and environmental microbiology, 63(7), 1997, pp. 2792-2797
In sporulating cultures of Bacillus thuringiensis subsp yunnanensis HD
977, two cell types are observed: cells forming only spores and cells
forming only crystals. Curing analysis suggested that the crystal prot
eins are plasmid encoded. Through plasmid transfer experiments, it was
established that a 103-MDa plasmid is involved in the crystal product
ion. Conjugal transfer of this plasmid to Cry(-) recipient cells of Ba
cillus thuringiensis subsp kurstaki HD73-26 conferred the ability to p
roduce crystals exclusively on asporogenous cells of the recipient, in
dicating that the 103-MDa plasmid mediates the unique regulation of Cr
y protein production. When the dipteran-specific cryIVB gene was intro
duced into wild-type (Cry(+)) and Cry(-) backgrounds of B-thuringiensi
s subsp yunnanensis by phage CP51ts45-mediated transduction, similar t
o all other B-thuringiensis strains, irregular crystals of CryIVB prot
ein were produced by spore-forming cells in both backgrounds. However,
the synthesis of the bipyramidal inclusions of B-thuringiensis subsp
yunnanensis was still limited only to asporogenous cells of the transd
uctant. Thus, it appears that the unique property of exclusive crystal
formation in asporogenous cells of B-thuringiensis subsp yunnanensis
is associated with the crystal protein gene(s) per se or its cis actin
g elements. As the crystals in B-thuringiensis subsp yunnanensis were
formed only in asporogenous cells, attempts were made to find out whet
her crystal formation had any inhibitory effect on sporulation. It was
observed that both Cry(+) and Cry(-) strains of B-thuringiensis subsp
yunnanensis (HD977 and HD977-1, respectively) exhibited comparable sp
orulation efficiencies. In addition, the Cry(-) B-thuringiensis subsp
kurstaki host (HD73-26) and its Cry(+) transconjugant (HD73-26-16), ex
pressing the B-thuringiensis subsp yunnanensis crystal protein, were a
lso comparable in their sporulation efficiencies, indicating that prod
uction of the crystal proteins of B-thuringiensis subsp yunnanensis do
es not affect the process of sporulation.