Microbial Symbioses with Humans - Urogenital Tracts and Their Microbes

6 important questions on Microbial Symbioses with Humans - Urogenital Tracts and Their Microbes

Explain how changes in pH can lead to urinary tract infections, focusing on specific bacteria involved.

Potential pathogens like Escherichia coli and Proteus mirabilis, normally present in small numbers in the urethra, can multiply in the urethra and cause urinary tract infections if conditions such as changes in pH occur. Proteus is particularly notorious as a urinary tract pathogen, generating ammonia from urea and raising urine pH, potentially triggering conditions like the formation of kidney stones.

Describe the microbial characteristics of the adult female vagina, highlighting the role of Lactobacillus acidophilus and changes in microbial composition throughout life stages.

The adult female vagina is weakly acidic (pH ∼5) and contains glycogen. Lactobacillus acidophilus, a resident organism, ferments glycogen, producing lactic acid that maintains a local acidic environment. Before puberty, L. acidophilus is absent, and the microbiota consists predominantly of staphylococci, streptococci, corynebacteria, and E. coli. After menopause, glycogen production ceases, the pH rises, and the microbiota resembles that found before puberty.

Discuss the diversity and dominance of lactobacilli in the vaginal microbiota, comparing it to microbial diversity in the gut or oral cavity.

Unlike the gut or oral cavity, the vaginal microbiota in healthy females is overwhelmingly dominated by lactobacilli. There are at least five types of "normal vaginal communities," with Lactobacillus spp. dominating. These types vary in Lactobacillus species and pH levels.
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Examine the types of "normal vaginal communities" and their characteristics, emphasizing the role of Lactobacillus species and pH levels.

There are five types of "normal vaginal communities" defined by dominance by L. crispatus, L. iners, L. reuteri, L. jensenii, or a more heterogeneous type with higher diversity. Lactobacillus spp., especially Lactobacillus acidophilus, dominate these communities. The L. crispatus type shows the lowest average pH (∼4.0), while the heterogeneous type shows the highest average pH (∼5.3).

Compare the microbial composition of the male and female urethra, emphasizing similarities and differences.

Species of Lactobacillus, Streptococcus, and Sneathia are commonly found in both the male and female urethra. However, the circumcised versus the uncircumcised penis can have different microbiota, with bacterial abundance typically much greater on the uncircumcised penis.

Discuss the influence of circumcision status on the microbiota of the penis, considering bacterial diversity and abundance.

Circumcision status influences bacterial abundance on the penis, with the uncircumcised penis typically having much greater bacterial abundance. The bacterial diversity of the penis is similar to that of the vagina, especially in sexual partners.

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