Isolation and
identification of two bacterial species (Genus: Bacillus) from flacherie-infected
larvae of Samia ricini
Kashyap Rajib Ratan and Brahma Dulur
Res. J. Biotech.; Vol. 20(8); 64-73;
doi: https://doi.org/10.25303/208rjbt064073; (2025)
Abstract
Samia ricini (Eri silkworm) is a commercially exploited, sericigenous lepidopteran
species of the northeastern State of India, Assam. The species is often contaminated
by various microbial pathogens and as a result, suffers from heavy mortality. Flacherie
is one type of microbial disease that causes 30%-100% crop loss annually in the
ericulture sector of Assam during summer. However, studies on the identification
and pathogenesis of bacteria in Samia ricini are lacking. The present study aims
to identify bacterial species involved in the flaccid condition of Samia ricini.
For this, hemolymph of infected 5th instar larvae was selected as inoculum and bacteria
were cultured and incubated in nutrient agar media at 370C for 48 hours. Distinct
colonies that grew on the culture media were subjected to identification through
morphological, biochemical and molecular methods.
The isolated DNA's colony morphology, biochemical tests and 16S rRNA sequencing
identified the isolates as Bacillus thuringiensis and Bacillus cereus. The current
study gives insight into the bacterial diversity responsible for flaccid conditions
in Samia ricini which might help to understand the mechanism of pathogenesis, disease
prognosis and colonization of different flacherie-causing bacteria in Samia ricini.
