Student Name Paper Analysis #1 : Constitutive Type VI Secretion System Expressio
ID: 143452 • Letter: S
Question
Student Name Paper Analysis #1 : Constitutive Type VI Secretion System Expression Gives Vibrio cholerae Intra- and Interspecific Competitive Advantages. D. Unterweger, M. Kitaoka, S. T. Miyatal, V Bachmann, T. M. Brooks, J. Moloney, O. Sosa, D. Silva, J. Duran-Gonzalez, D. Provenzano, and S. Pukatzki 1. What is the objective or hypothesis of this study? 2. What is the background/significance for doing this study? 3. Provide a brief summary of Figure 1. 4. Provide a brief summary of Figure 2. 5. Provide a brief summary of Figure 3Explanation / Answer
Objective: To study the type of T6SS regulation prevalent in the V. cholera isolates obtained from Rio Grande.
Background and significance: Along with the two main virulence factors i.e, watery diarrhea-cholera toxin and coregulated pilus toxin, which have been already implicated in Cholera induced diarrheal diseases, accessory toxins released by some strains of V. cholera have also been reported to be the virulence factor associated with the disease. One of the accessory virulence factor, Type VI secretion system (T6SS) confers cytotoxic effect against both prokaryotic and eukaryotic cells. The regulation of T6SS is highly controlled and is differentially expressed in different strains strongly influencing the pathogenicity associated with the strain. In the present study authors are keen in studying the expression and regulation of one of the potent virulence factor T6SS associated with the environmental strains obtained from Rio Grande. The result may have great implications in the awareness of public health and sanitation in the given region.
Brief summary of figure 1:
Here the authors went on to determine the virulence of 2 rough isolates DL2111 and DL2112 and two smooth isolates DL4211 and DL4215 for its ability to kill E. coli. They observed that both the smooth isolates are significantly much more virulent (pathogenic) and had killed more E. coli as compared to the rough isolates. The killing capacity of the smooth strains were almost comparable to the virulent strain V52 which served as a virulent control for the experiment.
Brief summary of figure 2:
In this experiment authors went on to determine if the cytotoxic effect observed in the previous experiment is mediated by T6SS. For this they ingeniously selected a system where T6SS mediated cytotoxicity is already established. They show that when the smooth isolates were incubated and plated with bacteria feeding amoebae (D. discoideum), number of plaques were significantly reduced when compared to rough isolates which indicated that the smooth isolates were effectively killing amoebae by established T6SS dependent cytotoxicity.
Brief summary of figure 3:
Western blot showing the differential expression of T6SS hallmark protein Hcp among the isolates obtained. We can clearly see the presence of Hcp protein in both pelleted and TCA precipitated supernatant obtained from smooth isolates DL4211 and DL4215. Whereas clear absence of the Hcp band in the lanes corresponding to rough isolates DL2111 and DL2112 indicates that the T6SS is not expressed in these isolates. The virulent V52 acted as a positive control for Hcp while levels of RNA-pol acted as the loading control for the experiment.