Bacillus thuringiensis in caterpillars and associated materials collected from protected tropical forests in northwestern Costa Rica

Abstract

Abstract. Bacillus thuringiensis (Bt) synthesizes crystalline inclusions that are toxic to caterpillars (Lepidoptera) and other orders of invertebrates. Materials associated with 37 caterpillars from 16 species, collected while feeding on 15 different species of host plants in dry, cloud and rain forests located in the Área de Conservación Guanacaste in northwestern Costa Rica, were examined for the presence of Bt. From a total of 101 derived samples, 25 Bt isolates were cultured: 56% from host plant leaves, 8% from caterpillar guts and 36% from caterpillar fecal pellets. Bt was isolated from at least one sample in 38% of the systems constituted by the food plant, gut and fecal pellets corresponding to a single caterpillar. Four different morphologies of crystalline inclusions were observed, with bipyramidal and irregular crystal morphologies being the most prevalent. Rev. Biol. Trop. 54(2): 265-271. Epub 2006 Jun 01.

Immune modulation enables a specialist insect to benefit from antibacterial withanolides in its host plant

“…Whether this dose is similar to a dose H. subflexa and H. virescens might encounter in a natural environment is difficult to evaluate. The few attempts to measure the density of Bt spores in nature646566 have documented a very patchy distribution.…”

Bacillus thuringiensis Is an Environmental Pathogen and Host-Specificity Has Developed as an Adaptation to Human-Generated Ecological Niches

“…Bt has been isolated from the phylloplane in natural or artificial ways [ 34 , 42 , 43 , 44 ]. It has been shown that Bt can reach this niche by rain splash from the soil to lower leaves [ 31 ], from soil as a result of being carried by germinating seeds [ 43 ], from animal feces such as those from insects or birds [ 34 , 36 ], and from dead insects [ 34 ].…”

“…Zhang et al [ 36 ] showed the presence of Bt in the intestinal tract of chickens, with the duodenum being the main portion colonized; moreover, it was verified that these animals kept releasing the bacterium through their feces for a certain time, even after removal of Bt from the diet. Similarly to vertebrates, Bt has been also isolated from fecal pellets of non-susceptible caterpillars from forests of conservation areas [ 44 ]. In another report, Bt germination in the alimentary tract was demonstrated in different invertebrates (e.g., earthworms), with sporulation occurring after defecation [ 8 ].…”