Arinze Okoli
Genok - Centre for Biosafety, Norway
Title: Application of Proteomics in the study of Microbial Physiology: taking advantage of changes in the microbe’s normal functions under stress conditions
Biography
Biography: Arinze Okoli
Abstract
Stress conditions cause microorganisms to adjust their normal functions to counter the deleterious effects of the stress. This
includes modulating relevant proteins in response to the stress. In our studies, we seek to decipher the message inherent in
the picture painted by the network of the modulated proteins, with the aim of understanding the physiology of the bacteria and
viruses. For example, under exposure to sub-lethal concentrations of the herbicide, glyphosate, and its breakdown product, amino
methyl phosphonic acid (AMPA), E .coli upregulated 18 and downregulated 14 proteins under glyphosate stress. Under AMPA
stress, the bacterium upregulated 32 and downregulated 8 proteins. E. faecalis upregulated 67 and downregulated 16 proteins under
glyphosate stress, but upregulated 172 and down-regulated 104 proteins under AMPA stress. For E. coli, majority of the regulated
proteins under glyphosate and AMPA stress where transport, stress response and nitrate metabolic proteins. Exposure of Helicobacter
hepaticus under the stress of bile –an antimicrobial agent which is produced in the liver, concentrated in the gallbladder and released
into the gut during digestion of fatty foods, resulted in the modulation of different proteins. In bovine, porcine or human bile, the
bacterium modulated differently the expression of several virulence determinants including the cytolethal distending toxin (CDT),
urease, superoxide dismutase, flagellin and ferritin. For example, superoxide dismutase was downregulated in the three types of bile;
CDT was downregulated in bovine and human bile, but was unaffected by porcine bile; urease was downregulated in bovine bile,
upregulated in porcine bile and unaffected in human bile. The data suggested that bile serves as an environmental cue for protein
expression by H. hepaticus, and may modulate its virulence factors. Genetic modification of organisms, e.g. insertion of unrelated
foreign gene into the genome of an organism (transgenesis) also can be considered a type of stress given that the organisms are forced
to adapt to the effects of the genetic manipulation. The introduction of the haemagglutinin and nucleoprotein genes of the H1N1
influenza virus into the genome of Modified Vaccinia virus Ankara resulted in the modulation of 32 virus encoded proteins that are
involved in various pathways of the virus replication. Overall, application of proteomics in conjunction with other complimentary
molecular biology tools, has enabled us to contribute towards understanding the physiology of these organism.