Sumários

Symbiotic host-bacteria interactions: the Sinorhizobium/legume symbiosis

7 Outubro 2019, 09:00 Jorge Humberto Gomes Leitão

The available sources of nitrogen were presented and discussed, focusing on the important role played by biological nitrogen fixation in natural ecosystems. The main groups of prokaryotic nitrogen fixers were presented. The symbiotic system Sinorhizobium/legume of nitrogen fixation was presented. The molecualr details of the interaction between the bacterium and the plant from initial mutual recognition until the formation of mature productive nodules were presented and discussed, with emphasis on the structures of flavenoids and Nod factors, and on the biosynthesis of the succinoglycan. 

Biochemical traits of the nitrogenase complex, on the regulation of the nif and fix genes were presented and discussed.


Examples of molecular appraches used to identify and characterize virulence factors from bacteria of the Burkholderia cepacia complex

2 Outubro 2019, 09:00 Jorge Humberto Gomes Leitão

Examples of strategies used  by researchers of the Biological Sciences Research group from IST to unveil the molecular determinants of virulence from bacteria of the Burkholderia cepacia complex were presented and discussed. The examples included the molecular biology of exopolysaccharide biosynthesis, the functional characterization of Hfq-like RNA chaperones, and the identification of sRNAs. 


Regulation of gene expression at the post-transcriptional level: non-coding regulatory RNAs and RNA chaperiones

30 Setembro 2019, 09:00 Jorge Humberto Gomes Leitão

General considerations on the classification of RNA  were presented and discussed. The roles of non-coding RNAs as regulators (sRNAs) in gene expression were presented and discussed, as well as the molecular mechanisms involved in the repression or activation of gene expression by sRNAs in bacteria. The roles played by the RNA chaperone were also presented and discussed. Examples of sRNAs and their roles in bacterial adaptation to stress, on virulence, biofilm formation, etc., were presented and discussed.


Qorum sensing and quorum quenching

25 Setembro 2019, 09:00 Jorge Humberto Gomes Leitão

The phenomena of regulation of gene expression by quorum sensing was presented and discussed, including the chemical nature of the signaling molecules. The differences between the quorum sensing regulatory circuits and molecules used by Gram-positive or Gram-negative bacteria were presented and discussed. Examples of phenotypes regulated by Quorum sensing were presented and discussed, including biofilm formation and virulence, among others. Examples of quorum sensing systems from Pseudomonas aeruginosa were presented and discussed. The concept of quorum quenching was presented, and examples were presented concerning antagonists and lactonases.


Two component regulatory systems

23 Setembro 2019, 09:00 Jorge Humberto Gomes Leitão

The composition and functioning of two component regulatory systems was detailed. Emphasis was given to the histidine kinase sensor and catalytic domains conformational changes and phosphorylation of the histidine residues. Specific examples of two component regulatory systems were presented and discussed, including the EnvZ/OmpR, PhoU/PhoR ArcA/ArcB. The roles on TCRS on the metabolic adaptation to the presence /absence of oxygen were presented and discussed.