Functional Significance of Insect Gut Bacteria and Their Role in Host Insect Processes, Development, and Crop Production

Abstract

It is well known that the use of insecticides is very effective in combating the immediate problem of insect attack on crops. But the recurrent use of the chemical insecticides is paving way to the 3R (residue, resurgence, and resistance) problems in food, in environment, and in insects. There is an alternative method for managing the insect pest problem in crop plants. The use of insect gut microbes serving as a biocontrol method to manage the insect pest problem is based on the concept of managing the BUG with BUG. To implement this concept, it should be clear about the type of microorganisms present in the host insect and their important contribution to the host insect success. Hence, the main objectives of this chapter are (1) to provide a brief overview of bacterial phylotypes present in the different orders of class Insecta and their functional role play in the host insect survival by protecting from the harmful effects of insecticides, biocontrol agents, toxic chemicals of host plant, etc., (2) to emphasize about the loss of gut microbes due to antibiotic treatment, which causes developmental deformities in the host insect, and (3) to address the potential of gut bacteria in the area of crop production with their multifaceted plant-growth-promoting (PGP) characteristics. To assess this, special emphasis is given to the bacterial phylotypes isolated from the cruciferous specialist diamondback moth – Plutella xylostella – and their significant characteristics such as antifungal activity through chitinase, β-1,3-gluconase activity, HCN, siderophore production, IAA and 1-aminocyclopropane-1-carboxylate deaminase activity, nitrogen fixation and solubilization of P and Zn, and oxidation of sulfur. Based on the literature reviewed in this chapter, it could be concluded that the use of gut microbe may serve as a novel avenue for crop, pest management, and production by improving their beneficial characteristics, for instance, chitinase and siderophore production.