Bacillus subtilis contains two small c-type cytochromes with homologous heme domains but different types of membrane anchors.

We demonstrate that the cccB gene, identified in the Bacillus subtilis genome sequence project, is the structural gene for a 10-kDa membrane-bound cytochrome c(551) lipoprotein described for the first time in B. subtilis. Apparently, CccB corresponds to cytochrome c(551) of the thermophilic bacterium Bacillus PS3. The heme domain of B. subtilis cytochrome c(551) is very similar to that of cytochrome c(550), a protein encoded by the cccA gene and anchored to the membrane by a single transmembrane polypeptide segment. Thus, B. subtilis contains two small, very similar, c-type cytochromes with different types of membrane anchors. The cccB gene is cotranscribed with the yvjA gene, and transcription is repressed by glucose. Mutants deleted for cccB or yvjA-cccB show no apparent growth, sporulation, or germination defect. YvjA is not required for the synthesis of cytochrome c(551), and its function remains unknown.

Partial isolation and some properties of enterotoxin produced by Bacillus cereus strains

Extracellular proteins produced by Bacillus cereus AL-42 and AL-15 were fractioned by chromatography on QAE-Sephadex and Sephadex G75. This last chromatographic process resulted in three peaks. The major peak showed vascular permeability activity to rabbits, lethality to mice, and cytotoxicity to Vero and Hela cells. The analysis by SDS-PAGE after ultrafiltration confirm recent findings that the enterotoxin is a compound with molecular mass > 30.000.

Evaluation of virulence factors in environmental isolates of Vibrio species

Strains of Vibrio parahaemolyticus, Vibrio fluvialis and Vibrio mimicus isolated from seafood and seawater were examined for characteristics related to infectivity, such as enzymatic activity and animal assays. All strains hydrolysed DNA, starch, gelatin and chitin. Variable results were obtained with the haemolysin, chondroitin, collagen, elastin and lecithin tests. Production of thermostable direct haemolysin by V. parahaemolyticus was detected in 7.1% strains derived from seafood and 2%from seawater. In the animal assays, strains of V. fluvialis showed positive results at skin PF (75%), mouse lethality (100%), but no fluid accumulation in the suckling mice model was noted. Concerning V. mimicus, results showed skin PF (100%), mouse lethality (100%) and fluid accumulation in suckling mice (66.6%).

Laboratory evaluation on pathogenic potentialities of Vibrio furnissii

Sixteen strains of Vibrio furnissii recovered from 16 Brazilian patients with diarrhea were screened for virulence-associated factors. All strains were non-invasive, non-fimbriated, and did not produce either enterotoxins or cholera-like toxin. In contrast, most were hemolytic on blood agar and their broth-culture supernatants damaged HeLa cell monolayers. These cytolysins, as accepted for other enteropathogenic members of the family Vibrionaceae, might be determinants of pathogenicity in V. furnissii-mediated enteritis.

Vibrio fluvialis attachs to but does not enter Hela cell monolayers

Considering the possibility that invasiveness could be a neglected factor of virulence in Vibrio fluvialis-linked enteritis, since a dysenteric form of the disease was seen in Bangladesh, we studied 12 Brazilian strains of the organism, six clinical and six environmental, to determine whether they might be able to enter into HeLa cell monolayers or would carry plasmids incidentally involved in invasiveness. Four human and two environmental isolates attached to but did not enter into the cells. Though five strains harbored plasmids,no relationship was found between the carriage of these genetic elements and adhesiveness.

Multilocus enzyme electrophoresis study of Bacillus sphaericus

Multilocus enzyme electrophoresis (MLEE) has been used in the study of some Bacillus species. In this work we applied MLEE and numerical analysis in the study of the Bacillus sphaericus group. B. sphaericus can be distinguished from other entomopathogenic Bacillus by a unique allele (NP-4). Within the species, all insect pathogens were recovered in the same phenetic cluster and all of these strains have the same band position (electrophoresis migration) on the agarose gel (ADH-2). The entomopathogenic group of B. sphaericus seems to be a clonal population, having two widespread frequent genotypes (zymovar 59 and zymovar 119).

Mechanism of action of Bacillus thuringiensis toxins

The selectivity of Bacillus thuringiensis toxins is determined both by the toxin structure and by factors inherent to the insect. These toxins contain distinct domains that appear to be functionally important in toxin binding to protein receptors in the midgut of susceptible insects, and the subsequent formation of a pore in the insect midgut epithelium. In this article features necessary for the insecticidal activity of these toxins are discussed. These include toxin structure, toxin processing in the insect midgut, the identification of toxin receptors in susceptible insects, and toxin pore formation in midgut cells. In addition a number of B. thuringiensis toxins act synergistically to exert their full insecticidal activity. This synergistic action is critical not only for expressing the insecticidal activity of these toxins, but could also play a role in delaying the onset of insect resistance.

Exploration of receptor binding of Bacillus thuringiensis toxins

Wild type and mutant toxins of Bacillus thuringiensis delta-endotoxins were examined for their binding to midgut brush border membrane vesicles (BBMV). CryIAa, CryIAb, and CryIAc were examined for their binding to Gypsy moth (Lymantria dispar) BBMV. The binding of CryIAa and CryIAc was directly correlated with their toxicity, while CryIAb was observed to have lower binding than expected from its toxicity. The latter observation confirms the observation of Wolfersberger (1990). The "rule" of reciprocity of binding and toxicity is apparently obeyed by CryIAa and CryIAc, but broken by CryIAb on L. dispar. Alanine substitutions were made in several positions of the putative loops of CryIAa to test the hypothesis that the loops are intimately involved in binding to the receptor. The mutant toxins showed minor shifts in heterologous binding to Bombyx mori BBMV, but not enough to conclude that the residues chosen play critical roles in receptor binding.

Biochemistry and mode of action of the Bacillus sphaericus toxins

Bacillus sphaericus produces at least two toxins which are highly toxic to mosquito larvae. The binary toxin, which is comprised of proteins of 51.4 and 41.9 kDa, is present in all highly insecticidal strains. The 100 kDa SSII-1 toxin is present in most highly insecticidal as well as the weakly insecticidal strains. The current status of studies on biochemistry and mode of action of these toxins is reviewed.

Bacillus and Serratia species for Scarab control

Few microorganisms are commercially available for use against white grubs (larvae of Scarabaeidae). Entomopathogenic bacteria, particularly Bacillus popilliae, have been used the longest for white grub suppression. Other bacteria, namely B. thuringiensis and Serratia spp. offer promise for future control. This papes examines two genera of bacteria (Bacillus and Serratia) from the historical and current perspective. Bacillus popilliae, the firs microbial control agent registered in the United States, has a long history of use in suppressing populations of the Japanese beetle, Popillia japonica. However, lack of in vitro production and the slow and sporadic nature of its activity, severely limits its utilization. B. thuringiensis, the most widely used microbial pesticide, has not been used for scarab, control. However, strains with scarab activity have recently been discovered. Scarab larvae have been collected in the United States with signs and symptoms similar to those characteristic of amber disease (caused by Serratia entomophila) in the New Zealand grass grub, Costelytra zealandica. A total of 147 bacteria have been obtained from the digestive tracts of larvae of the Japanese beetle and masked chafers, Cyclocephala spp., as well as from larvae and soil collected in Japan and China. Seventy five of these have been identified as Serratia spp. Most (40) of the remaining bacteria are in the genus Enterobacter. A majority of the bacteria (73) and of the Serratia (38) came from P. japonica.

Some environmental and biological factors influencing the activity of entomopathogenic Bacillus on mosquito larvae in Brazil

The influence of environmental and biological factors on the efficacy of Bacillus thuringiensis serovar israelensis and B. sphaericus as mosquito larvicides are reviewed. The importance of strain dependence, cultivating media/methods, mosquito species/specificity, formulations and their relation to mosquito feeding habits, as well as temperature, solar exposure, larval density and concomitant presence of other aquatic organisms are addressed with reference to the present status of knowledge in Brazil.