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DTSTART:20191027T020000
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DTSTAMP:20260404T070130Z
UID:5cb04aac9059c899683116@ist.ac.at
DTSTART:20190415T110000
DTEND:20190415T120000
DESCRIPTION:Speaker: Gaurav Diwan\nhosted by Fyodor Kondrashov\nAbstract: T
 ranslation is a central cellular process across the tree of life. Bacteria
 \, which form a major portion of this tree\, exhibit tremendous phenotypic
  and genomic diversity. An important question is how the process of transl
 ation has evolved given this large diversity of bacteria. So far\, studies
  have analysed the evolution of codon usage\, tRNA genes and tRNA modifica
 tions in only a few bacteria. Thus\, a systematic and comprehensive study 
 of these aspects across a large number of bacteria was lacking. I studied 
 the evolution of three traits affecting translation elongation: tRNA modif
 ications\, tRNA gene complement\, and internal Shine Dalgarno (SD)-like mo
 tifs\, across a large number of bacteria. All three traits were correlated
  with the GC content of bacteria. For instance\, high GC organisms possess
 ed a larger set of tRNA genes and as a result\, some high GC clades lost t
 RNA modifications. This is probably because a larger set of tRNA weakened 
 selection on tRNA modifications and led to their loss. Differently AT rich
  bacteria lost several tRNA genes as well as tRNA modifications. This indi
 cated that AT rich bacteria are unable to decode all 61 sense codons. Inte
 restingly\, across several species\, the codons that were unreadable were 
 used less frequently as compared with  synonymous codons. Unreadable codon
 s were also lost over evolutionary time indicating that codon use evolves 
 in response to the gain/loss of tRNA genes. Finally\, I found that the fre
 quency of internal SD like motifs was correlated with the GC content of ba
 cteria. However\, the selection to avoid internal SD like motifs was highe
 r for bacteria with high GC content. Interestingly\, mesophiles and N-term
 inal regions of genes also showed a distinct signature of avoiding interna
 l SD like motifs. This indicated that the frequency of internal SD like mo
 tifs is governed by multiple selection pressures. Overall\, my thesis pres
 ents a nuanced view of the evolution of bacterial translation and demonstr
 ates that translation mechanisms in diverse bacteria are extremely variabl
 e. I also describe interesting case studies for future work that could lea
 d to further understanding of the evolution of bacterial translation.
LOCATION:Mondi Seminar Room 3\, Central Building\, ISTA
ORGANIZER:amally@ist.ac.at
SUMMARY:Gaurav Diwan: Computational analyses of the evolution of bacterial 
 translation
URL:https://talks-calendar.ista.ac.at/events/1919
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