also been reported by Fisher and Rosner (1959), 
Ignoffo (1973), Heimpel (1971), Krieg and Franz 
(1959), Lemoigne (1956), Steinhaus (1951), and 
Lamanna and Jones (1963) and include virulence 
in mice, persistence in blood of mammals, 
pathogenicity by parenteral administration, inha¬ 
lation toxicity in mice, allergenicity in guinea pigs, 
inhalation and ingestion by human volunteers and 
acute oral toxicity. 
Bacillus morltai. a pathogen for houseflies and 
mosquitoes, has been manufactured by private 
industry in Japan and investigations have been 
made on the effectiveness of its product in the field 
and the safety for warm-blooded animals (Burger- 
jon, 1973; Fujiyoshi, 1973). 6. morltai is not patho¬ 
genic for the silkworm, honeybee, mouse, rat, 
rabbit, bird, fish, pig, or cattle. Malignancy and car¬ 
cinogenicity were also examined and finally the 
safety was checked by human experiments with 
negative results. 
3. Features Relating to Recombinant DNA 
Experimentation 
Entomopathogenic bacteria of pest insect spe¬ 
cies offer a unique and relatively safe model sys¬ 
tem for studying the effects of recombinant DNA 
research using procaryotic - and possibly eucary- 
otic - derived DNA. The entomopathogenic bacte¬ 
ria are primarily species or genus "specific" and 
several have been tested for their safety in regard 
to vertebrate and non-target organisms. It is sug¬ 
gested that increased recombinant DNA research 
emphasis be focused on these bacteria which 
have some safety advantages over some other 
bacteria currently used as recombinant DNA 
tools. Envisaged in research among entomopa¬ 
thogenic bacteria are possible applications of in 
vitro gene splicing and recombinant DNA cloning 
to (1) expand the insect pest host-spectrum of 
existing insect pathogens, (2) develop new and 
more potent strains of pest insect pathogens, (3) 
improve the physiological tolerance and epidemi¬ 
ological properties of these bacteria, and (4) facili¬ 
tate the in vitro commercial production of the more 
fastidious insect pathogens by expanding the 
range of in vitro substrates upon which they can 
grow. 
The use and approval of appropriate plasmid or 
bacteriophage vectors is a primary consideration 
in this research. Plasmids have been identified in 
many bacteria (Cohen, 1976; Helenski and Cle- 
well, 1971; Flelinski, 1 973). A large variety of spe¬ 
cific biochemical functions such as fertility, 
resistance to antimicrobial drugs, production of 
bacteriocins, production of toxins, etc., have been 
attributed to these genetic elements. We have 
recently examined four entomopathogenic bacte¬ 
ria for extrachromosomal DNA molecules which 
are summarized in Table 1. 
Table 1 
Number and size estimation of extrachromosomal DNA elements of Bacillus thuringlensis var. kurstaki, 
var. sotto, var. flnltmus, and Bacillus popilliae isolated by agarose gel electrophoresis. 
B. t. var kurstaki 
B. t. var sotto 
B. t. var 
finitimus 
B. popilliae 
>50 X 7 06(a) 
~45 X 106 
-29.9 X 106 
-17.1 X 106 
-23.5 X 106 
>50 X 10^(2) 
7.4 X 106 
4.2 X 106 
3.9 X 106 
3.6 X 106 
1.1 X 106 
0.87 X 106 
0.98 X 106 
4.45 X 106 
0.80 X 106 
0,80 X 106 
0.79 X 106 
0,74 X 106 
0.62 X 106 
0.58 X 106 
a/ Daltons; size estimations were determined from a standard curve (full log; 3 cycles by 1 cycle) estimated by their mobilities relative 
(R() to the DNA standards included in the agarose gels. 
5 
