An Investigation of Bacillus thuringiensis in Rectal-Collected Fecal Samples of Cows

Abstract

In order to better understand the range and role of Bacillus thuringiensis (Bt) and its toxins in nature, we have undertaken a study of Bt taken directly from the rectum of 117 cows from 37 farms on the Caribbean island of Trinidad. Thirty-seven fecal samples (32%) were found to contain at least one Bt. Generally only one or two isolates with a particular crystal morphology were isolated from any one sample, however, a few samples contained more, up to 11 isolates, suggesting post-ingestion amplification. Bioassays using larvae of Musca domestica, Caenorhabditis elegans and Tetrahymena pyriformis showed no observable toxicity in gross bioassays. Very small dot-like parasporal bodies, not generally characteristic of Bt, were isolated from 44% of the samples, which in many instances appeared unstable and whose relation to Bt Cry protein-containing parasporal bodies is unknown. In conclusion, we find little evidence for a host adapted strain of Bt in the cows examined, nor toxicity to organisms that might logically be associated with either the cow or its feces. The presence of a large number of isolates containing small dot-like parasporal bodies, possibly either poly-beta-hydroxybutyrate storage bodies or Cry proteins, was unexpected and merits further investigation.

The quorum sensing system NprR-NprRB contributes to spreading and fitness in colony biofilms ofBacillus thuringiensis

“…In turn, the mechanisms that B. thuringiensis uses to spread in soil or other habitats are still unknown. It has been reported that it occurs mainly passively by the action of rain, wind, water, plant growth, and by the presence of spores in insect cuticles and feces (74)(75)(76)(77)(78)(79)(80)(81). However, B. thuringiensis can also colonize diverse tissues of plants, being found mainly in the roots where exudates rich in carbohydrates and amino acids are secreted and favor its growth (82).…”

Dissecting the Environmental Consequences of Bacillus thuringiensis Application for Natural Ecosystems

“…So far, Bt strains have been isolated from the soils having not experienced exposure to Bt -based products [ 55 , 56 , 57 , 58 , 59 ]. The total soil Bt population is thus constituted by natural soilborne strains, strains introduced with the application of pesticide, and strains transferred from other local biotopes, such as phyllosphere, insect cadavers, or animal feces [ 60 , 61 , 62 , 63 ].…”

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

“…However, it has been found that Bt spores can pass through the digestive tract of vertebrates and invertebrate organisms, reaching their feces. In these circumstances, they find favorable conditions for germination, and so, become capable of being dispersed in the environment through migration of these animals [ 8 , 33 , 34 , 35 , 36 ].…”

“…For instance, Wilcks et al [ 33 ] demonstrated Bt ’s capability of colonizing the whole intestinal tract of germ-free rats, in high concentrations and in a stable form; Bt grew vegetatively for various generations (>90% of Bt population) before sporulation and elimination through their feces. Ammons et al [ 35 ] reported the presence of Bt in rectal samples from milk cows, with indication that multiplication of Bt cells had occurred in the digestive tract of these animals. 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.…”