B Babesia Bacillus sphaericus A genus of Protozoa that is transmitted to animals colin berry by ticks. Cardiff University, Cardiff, Wales, United Babesiosis Kingdom Piroplasmosis The bacterium Bacillus sphaericus is best-known to entomologists because of the toxicity of some Babesiosis strains to the larval stages of mosquitoes. This tox- icity will be examined below but first, some con- Several related diseases caused by infection sideration of the taxonomic group that is known with Babesia protozoans, and transmitted by as “Bacillus sphaericus” is necessary. ticks. Piroplasmosis Taxonomy Identification of a bacterium as aB. sphaericus iso- Bacillary Paralysis late is based on relatively few morphological fea- tures (e.g., the possession of a spherical terminal A disease of silkworm larvae caused by ingestion spore) and a limited number of biochemical tests of spores and parasporal crystals of Bacillus (e.g., inability to ferment sugars). As a result, the thuringiensis. classification contains a heterogeneous collection of strains and it has been shown that, at the DNA level, these can be divided into five major homol- Bacillus larvae (=Paenibacillus ogy groups (groups I-V), each of which could be larvae; Bacteria) considered as a separate species. All of the insecti- cidal strains of B. sphaericus are found within a The bacterium responsible for causing American subdivision of one of these groups – Group IIA; foulbrood in honey bees; it is now known as however, not all strains that fall within this group Paenibacillus larvae. are insecticidal. It is the insecticidal strains of American Foulbrood B. sphaericus and their properties that will be con- Paenibacillus sidered further below. 346 B Bacillus sphaericus Target Range The Insecticidal Toxins Bacillus sphaericus is toxic to a small range of dip- Insecticidal strains of B. sphaericus owe this teran target insects, principally mosquitoes (with property to the fact that they produce protein some possible activity against Chironomus spe- toxins. To date, several different types of toxins cies). Within the mosquitoes, B. sphaericus is often have been identified. The names of these toxins, seen as most active against Culex species with along with notes on their mechanisms of action, lower activity against Anopheles, Mansonia and are given in the table below. Psorophora and lowest activity against Aedes spe- All the toxins except sphaericolysin exert cies. However, these generalizations should be their effects on the gut of the aquatic larval form treated with caution as some Aedes species are as of the mosquito after ingestion of the bacterium. sensitive as Culex species so that susceptibility The binary toxin (Bin) is produced on sporula- must be judged at the species level and not by tion whereupon it is deposited in spore-associ- genus. In addition, activity of a B. sphaericus toxin ated crystal As shown in the figure of B. has been reported against the German cockroach, sphaericus, (Fig. 1) the spore is the round body at Blattela germanica. the top, the crystal is the grey, rhomboid body in the center, and both are contained within the elongated exosporium. Once eaten by a mos- quito larva, the crystal dissolves and its two com- Field Use ponent proteins (BinA -42 kDa and BinB -51 kDa) are able to bind to specific receptors in the Bacillus sphaericus strains have been used in gut before lysing the cell by pore formation. control programs worldwide to suppress mos- Note: although the Bin proteins form a spore quito populations that are of nuisance or public associated toxin crystal, they are not related to health importance. For this purpose, only strains the majority of the crystal-associated Cry and showing high-level, spore-associated toxicity Cyt toxins of Bacillus thuringiensis. Most highly are used (e.g., VectoLex® and Spherimos® from toxic B. sphaericus strains produce only the Bin Valent BioSciences, or Sphaerus® from Bthek toxin in association with spores (Mtx toxins are Ltda). For production of maximum toxicity, as produced only in vegetative cells and in very low well as for ease of production and storage, such quantities). The existence of only one toxin in formulations are produced from fully sporu- spores applied in mosquito control programs in lated B. sphaericus cultures that can be sprayed the field can lead to resistance in target popula- or applied as blocks or granules that disperse in tions. A few strains of B. sphaericus can over- the aqueous habitats. come this resistance in Culex mosquitoes. These Bacillus sphaericus, Table 1 Toxins of Bacillus sphaericus Toxin (molecular wt.) Mechanism of action Reference Bin (51 and 42 kDa) Pore formation Oei et al. (1992), Schwartz et al. (2001) Mtx1 (100 kDa) ADP-ribosylation Thanabalu et al. (1993) Mtx2 (31.8 kDa) Pore formation Thanabalu and Porter (1996) Mtx3 (35.8 kDa) Pore formation Liu et al. (1996) Cry48/Cry49 (136 and 53 kDa) Pore formation Jones et al. (2007) Sphaericolysin (53 kDa) Pore formation Nishwaki et al. (2007) Bacillus sphaericus B 347 References Ahmed I, Yokota A, Yamozoe A, Fujiwara T (2007) Proposal of Lysinibacillus boronitolerans gen. nov. sp. nov., and trans- fer of Bacillus fusiformis to Lysinibacillus fusiformis comb. nov. and Bacillus sphaericus to Lysinibacillus sphaericus com. nov. Int J Syst Evol Microbiol 57:1117–1125 Jones GW, Nielsen-Leroux C, Yang Y, Yuan Z, Dumas VF, Mon- nerat RG, Berry C (2007) A new Cry toxin with a unique two-component dependency from Bacillus sphaeriucs. FASEB J 21:4112–4120 Krych VK, Johnson JL, Yousten AA (1980) Deoxyribonucleic acid homologies among strains of Bacillus sphaericus. Int J Syst Bacteriol 30:476–484 Liu J-W, Porter AG, Wee BY, Thanabalu T (1996) New gene from nine Bacillus sphaericus strains encoding highly conserved 35.8-kilodalton mosquitocidal toxins. Appl Environ Microbiol 62:2174–2176 Nielsen-LeRoux C, Rao DR, Murphy JR, Carron A, Mani TR, Hamon S, Mulla MS (2001) Various levels of cross- resistance to Bacillus sphaericus strains in Culex pipiens (Diptera: Culicidae) colonies resistant to B. sphaericus strain 2362. Appl Environ Microbiol 67:5049–5054 Nishiwaki H, Nakashima K, Ishida C, Kawamura T, Matsuda K (2007) Cloning, functional characterization, and mode of action of a novel insecticidal pore-forming toxin, sphaericolysin, produced by Bacillus sphaericus. Appl Environ Microbiol 73:3404–3411 Oei C, Hindley J, Berry C (1992) Binding of purified Bacillus sphaericus binary toxin and its deletion derivatives to Culex quinquefasciatus gut: elucidation of functional binding domains. J Gen Microbiol 138:1515–1526 Schwartz J-L, Potvin L, Coux F, Charles J-F, Berry C, Bacillus sphaericus, Figure 1 Bacillus sphaericus. Humphreys MJ, Jones AF, Bernhart I, Dalla Serra M, Menestrina G (2001) Permeabilization of model lipid (Photo courtesy of Dr. J.F. Charles.) membranes by Bacillus sphaericus mosquitocidal binary toxin and its individual components. J Membr Biol 184:171–183 Silva-Filha MH, Nielsen-LeRoux C, Charles J-F (1999) Iden- strains produce a novel toxin pair, Cry48/Cry49, tification of the receptor for Bacillus sphaericus crystal which are deposited as crystals outside the exo- toxin in the brush border membrane of the mosquito sporium. The Cry48 protein is related to 3-do- Culex pipiens (Diptera: Culicidae). Insect Biochem Mol Biol 29:711–721 main Cry toxins of B. thuringiensis while Cry49 Silva-Filha M-H, Regis L, Nielsen-LeRoux C, Charles JF is related to the Bin proteins. Both components (1995) Low-level resistance to Bacillus sphaericus in a are required for toxicity to Culex larvae and do field-treated population ofCulex quinquefasciatus (Dip- not appear to kill other insects (including Anoph- tera: Culicidae). J Econ Entomol 88:525–530 Thanabalu T, Berry C, Hindley J (1993) Cytotoxicity and eles and Aedes mosquitoes). ADP-ribosylating activity of the mosquitocidal Despite reports of resistance developing in toxin from Bacillus sphaericus SSII-1: Possible roles mosquito populations, careful use of this bacte- of the 27- and 70-kilodalton peptides. J Bacteriol rium is likely to enable the continued favorable 175:2314–2320 Thanabalu T, Porter AG (1996) A Bacillus sphaericus use of this product for integrated control programs gene encoding a novel type of mosquitocidal toxin in the field. of 31.8 kDa. Gene 170:85–89 348 B Bacillus thuringiensis Yuan Z, Zhang YM, Cai QX, Liu EY (2000) High-level field farms. Additional B. thuringiensis isolates have been resistance to Bacillus sphaericus C3–41 in Culex detected in various insectaries, stored product envi- quinquefasciatus from Southern China. Biocontrol Sci Technol 10:41–49 ronments, and grain processing facilities. Studies have suggested that B. thuringiensis is a normal inhabitant of the foliage of plants. However, the soil Bacillus thuringiensis habitat has been the primary source for isolating novel B. thuringiensis isolates. Whether or not B. thu- Bacillus thuringiensis was initially described early ringiensis undergoes saprophytic development in in the 1800s as the causal agent of the “sotto bacil- soil is unclear. Many bacilli considered to be close lus disease” of the silkworm Bombyx mori. Later relatives of B. thuringiensis are known to inhabit studies by Aoki in 1915 demonstrated that this hypogean environments. Presently, it has been esti- bacterial agent produced a crystalline toxic mate- mated that over 60,000 isolates of B. thuringiensis are rial at sporulation. In 1911, Berliner isolated the being maintained in culture collections worldwide. type species Bacillus thuringiensis var. thuringien- Members of B. thuringiensis are rod-shaped sis from the flour moth in the province of Thurin- (1.0–1.2 by 3–5 microns), gram positive, facultative gia, Germany. Following this report, a series of anaerobes which utilize carbohydrates as preferred papers demonstrated that B. thuringiensis could energy sources. Classification based on 16S rRNA infect and kill a variety of lepidopteran host insects. sequence data clusters B. thuringiensis with B. cereus, Until the 1970s, all B.