主题：Bt菌在自然界里的存在，是否仅仅限于土壤 -- 王二狗

从人开始吃菜那年就开始吃这玩意了。牛马驴骡更是没少吃这些东西，它们做饭之前不摘菜呀。

没有人类折腾， 不会天然到草上， 菜上的。

Novel variants of Bacillus thuringiensis were isolated from the phylloplane of deciduous and conifer trees as well as of other plants. These isolates displayed a range of toxicity towards Trichoplusia ni. Immunoblot and toxin protein analysis indicate that these strains included representatives of the three principal B. thuringiensis pathotypes active against larvae of the orders Lepidoptera, Diptera, and Coleoptera. We propose that B. thuringiensis be considered part of the common leaf microflora of many plants.

Bacillus thuringiensis was isolated from 36 of 50 residue samples obtained from an animal feed mill (a stored-product environment). Of 710 selected colonies having Bacillus cereus-B. thuringiensis morphology isolated from the samples, 477 were classified as B. thuringiensis because of production of parasporal δ-endotoxin crystals. There was a diverse population of B. thuringiensis, as revealed by differentiation of the isolates into 36 subgroups by using (i) their spectra of toxicity to the lepidopterans Heliothis virescens, Pieris brassicae, and Spodoptera littoralis and the dipteran Aedes aegypti and (ii) their parasporal crystal morphology. A total of 55% of the isolates were not toxic to any of these insects at the concentrations used in the bioassays; 40% of all isolates were toxic to one or more of the Lepidoptera; and 20, 1, and 1% of the isolates were toxic to only P. brassicae, H. virescens, and S. littoralis, respectively. The most frequent toxicity was toxicity to P. brassicae (36% of all isolates); 18% of the isolates were toxic to A. aegypti (5% exclusively), 10% were toxic to H. virescens, and 4% were toxic to S. littoralis. Toxicity to P. brassicae was more often linked with toxicity to H. virescens than with toxicity to S. littoralis. The frequency of toxicity was significantly greater in isolates that produced bipyramidal crystals than in isolates that produced irregular pointed, irregular spherical, rectangular, or spherical crystals.

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 rea 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.

Abstract

Bacillus thuringiensiswas isolated from natural samples collected from 80 countries. The majority, 45% of the 5303 isolates, originated from stored products, with 25% originating from soil. The materials richest in isolates active in insects were mushroom compost and stored products. The proportion with bipyramidal-shaped crystals was 46%, while among the range of other shapes 14% were spherical and 4% rectangular. The largest proportion of isolates, 45%, was found in the United Kingdom with the majority originating from stored mills, which import produce from all over the world; 22% came from North America. Using single-dose assays, 44% of the isolates killed less than 25% of larvae of all four Lepidoptera tested,Heliothis virescens, Pieris brassicae, Spodoptera littoralis,andAgrotis ypsilon.Among isolates killing more than 25% of the larvae, every combination of activities of the 16 possible against these 4 insects was found, in proportions ranging from 0.6 to 14.5%, suggesting considerable diversity of insect activity. The 44% of strains with little or no activity to Lepidoptera (<25% mortality) included strains selectively active against Diptera and Coleoptera. An analysis of activity using one representative species from each of the three orders of insectsH. virescens, Aedes aegypti,andPhaedon cochleariaeshowed 48.8% of strains to be inactive (<25% mortality) in all three, with 1.2 to 14.6% active in the other 7 possible combinations. For an analysis of geographical origins of insect activity, 3 species (P. cochleariae, S. littoralis,andH. virescens) were chosen with susceptibility to different δ-endotoxins. With one exception, activity did not appear to be correlated with origin, indicating a relatively ubiquitous distribution of the selected activities and ofB. thuringiensisin general. The worldwide spread and evolution of this insect pathogen and its different types are discussed in relation to geographical origin and source materials, as well as possible interaction with other bacteria.

Using acetate selection to screen dust samples and cadavers of insect, Bacillus thuringiensis was isolated from 122 of 413 samples obtained from various warehouses, processing facilities and animal feed mills. Abundance of B. thuringiensis in the settled dust samples of different origins was different. Among them, B. thuringiensis were most abundant in the settled dust samples from warehouses storing rice bran and gunny-bag, in which 46 and 50% of samples contained B. thuringiensis, respectively. The B. thuringiensis in samples from mountainous region and hilly country were more abundant than that from lowland areas, in which 41 and 20% of samples contained B. thuringiensis, respectively. These B. thuringiensis isolates belonged to serotypes H3, H4, H5, H7, H8, H10, H23 and H27. Among them, serotypes H4 and H5 were most abundant and amounted to 36 and 24% of isolates, respectively. The B. thuringiensis from different types of warehouses and regions was different in terms of H-serotype. There is rich diversity of toxicity to insects in B. thuringiensis isolates from warehouses; 58 and 71% of the isolates were toxic to larvae of Plodia interpunctella and Spodoptera exigua, respectively, causing more than 60% mortality. Most isolates were not toxic to Phaedon brassicae and Culexpipiens fatigans; only one isolate was highly toxic, causing more than 90% mortality to both species.