A Study of Antibacterial Immune Response of Drosophila Melanogaster in Relation to Life-History Related Traits

Khan, Imroze (2012) A Study of Antibacterial Immune Response of Drosophila Melanogaster in Relation to Life-History Related Traits. PhD thesis, Indian Institute of Science Education and Research Kolkata.

PDF (PhD Thesis of Imroze Khan) Imroze-Khan-PhD-Thesis.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

The goal of this thesis was two-fold: to relate several life-history events to antibacterial immunity and to identify the molecular changes associated with bacterial infection using Drosophila melanogaster as model host and Serratia marcescens as model pathogen. I have evaluated antibacterial immune response of Drosophila melanogaster in relation to several events of its life-history such as differential response to bacterial infection by the two sexes, reproductive fitness, survivorship, mate identity and senescence which indicates that host immune response is not only about sensing invading pathogens and succesfilly defending the host only. Several life-history events should be taken into account while addressing holistic view of functional immune response in relation to its life-history consequences. For example, antibacterial immune response may differ in females depending upon the male phenotype they mate with. Functional immune response raised against invading pathogen may change with the progression of age in both the sexes. Bacterial infection may lead to reduction of one component of total fitness- post infection survival- equally in either sex. However, another component of total fitness- reproductive success- was affected differentially in either sex. Thus the total fitness cost paid by each sex towards bacterial infection can be potentially different, which may have important implications in the evolution of antibacterial immunity. In addition, to understand the model host-pathogen interaction better, I also addressed the associated host molecular changes in the light of the effect of infection on the major adult fitness components. Hence, the present thesis majorly considered immune defence as an important component of fitness. While vast amount research has been directed towards interaction between parasites and their hosts per se I have focussed majorly on host immunity in the lifehistory perspective. I propose that it is extremely important in order to understand the holistic picture of host immune response in relation to other essential components of life-history and evolution of immunity. The present thesis addresses few of these events, although, there are many that warrants future investigation to understand evolutionary ecology of immunity better.

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