Isolation and Identification of gut bacteria from white grubs Anomala dorsalis and Lepidiota mansueta Larvae (Coleoptera: Scarabaeidae)

Abstract

The guts of most insects harbor nonpathogenic microorganisms. Recent work suggests that gut microbiota not only provide nutrients, but also involve in the development and maintenance of the host immune system. However, the complexity, dynamics and types of interactions between the insect hosts and their gut microbiota are far from being well understood. White grub is a polyphagous and nefarious pest of specific significance as it adversely affects the economic status of the farmers. This study aimed to explore the aerobic and anaerobic gut bacterial flora of the larvae of two white grub pests, Anomala dorsalis Fabricius and Lepidiota mansueta Burmeister (Coleoptera: Scarabaeidae) of different insect gut Segments through cultivation-dependent approaches coupled with 16S rRNA gene analysis. The results revealed that twenty one out of 23 gut bacterial isolates from the guts of larvae of A. dorsalis, cultured under aerobic condition belonged to Firmicutes and only two types viz, Vibrio rumoiensis and Enterobacter xiangfangensis which were detected from rectum belonged to Proteobacteria. The highest percentage (35%) isolates were from Bacillus sp followed by Bacillus subtilis and Bacillus aerophilus with 22 percentages of occurrences. Whereas, Intestinal bacteria of L. mansueta larvae cultured under
anaerobic condition were classified into two groups: Bacteroidetes and Proteobacteria. Two bacterial phylotypes belonging to Bacteroidetes were Chryseobacterium sp and Dysgonomonas termitidis which were found in midgut and rectum while the other remaining two isolates viz., Enterobacter sp from midgut and Comamonas sp from fermentation chamber belonged to Proteobacteria. Furthermore, the colony count was higher on Nutrient Agar media with a mean of (225.56 x1010cfu/ml) followed by Luria Bertani Agar and Actinomyces Agar irrespective of gut segments. On Nutrient agar, the fermentation chamber had the highest mean count of 298.00x1010cfu/ml followed by hindgut (242.40x1010cfu/ml) and rectum (224.80 x1010cfu/ml), Therefore, the highest colony count was
recorded on the fourth day and increased incubation time increased colony count on the growth medium.The results demonstrated that a core microbial community of this insect species. Understanding the functional role of these gut bacterial isolates may pave the way for developing novel pest control strategies.