Test on Understanding the Human Microbiome

Question 1: MALDI utilizes a laser energy absorbing matrix to produce ions from molecules with significant fragmentation.

A. Ano

B. Ne

Explanation: MALDI produces ions from molecules with minimal fragmentation.

Question 2: According to the provided materials, what is the role of chromatographic steps in a conventional untargeted metabolomics workflow?

A. To produce ions from molecules using a laser energy absorbing matrix.

B. To deflect charged particles along a circular path proportional to their mass to charge ratio.

C. To separate metabolites before they are ionized and analyzed using mass spectrometry.

D. To extract small-molecule metabolites from the sample matrix.

Explanation: The study materials describe the conventional untargeted metabolomics workflow as: 'Small - molecule metabolites are extracted from the sample matrix. Metabolites are separated using chromatographic steps, ionized, and analyzed using MS.' This indicates that the role of chromatographic steps is to separate metabolites prior to their ionization and analysis by mass spectrometry.

Question 3: Pks+ E. coli promote the formation of tumors in an inflamed environment.

A. Ano

B. Ne

Explanation: Pks + E. coli promote tumorigenesis in an inflamed environment.

Question 4: Based on the study materials, which of the following is a direct mechanism by which colibactin from Escherichia coli contributes to carcinogenesis?

A. It causes double-stranded DNA damage in mammalian cells.

B. It blocks the function of human tumour suppressor proteins like p53.

C. It indirectly damages host cell DNA by eliciting high levels of reactive oxygen species.

D. It exclusively leads to deletion of thymine nucleotides in a string of thymines.

Explanation: The study materials explicitly state that colibactin expressed by B2 group of Escherichia coli "can cause double-stranded DNA damage in mammalian cells." Blocking tumour suppressor proteins is attributed to human papillomaviruses (HPV), and eliciting high levels of reactive oxygen species is attributed to Bacteroides fragilis toxin (BFT). While colibactin does lead to deletion of thymine nucleotides as one type of mutation, the materials also mention single-base substitutions and the overarching mechanism of damage as double-stranded DNA damage, making option 3 too narrow and inaccurate due to the word "exclusively".

Question 5: The genetic variant rs373863828 in Samoans is linked to less efficient fat storage.

A. Ano

B. Ne

Explanation: The study materials indicate that the genetic variant rs373863828 in Samoans is linked to more efficient fat storage, not less efficient.