Microbiology

Mary Mallon, also known as 'Typhoid Mary', was a carrier of the typhoid fever bacteria and unknowingly spread it through the food she prepared for others.

Step 1: Identify the pathogen for each disease.
Gonorrhea: Caused by the bacterium Neisseria gonorrhoeae, which is a gram-negative coccus.
Syphilis: Caused by the bacterium Treponema pallidum, which is a spirochete.
Trichomoniasis: Caused by the protozoan Trichomonas vaginalis.
Chlamydiasis: Caused by the bacterium Chlamydia trachomatis, which is an obligate intracellular parasite.
Step 2: Determine which disease is caused by a spirochete bacterium.
Based on Step 1, Syphilis is caused by Treponema pallidum, which is a spirochete bacterium. Step 3: Conclude the correct option.
Therefore, the spirochete bacterium causes Syphilis in human beings.

\textit{Giardia} is a flagellated protozoan parasite belonging to phylum Mastigophora. It causes giardiasis, a diarrheal disease in humans. The organism has a bilaterally symmetrical pear-shaped body with: - Two nuclei - A ventral adhesive disc - Eight flagella arranged in four pairs (anterior, posterior, caudal, and ventral) These flagella are essential for locomotion and attachment to the host’s intestinal wall. The number of flagella is a distinctive feature used in classification and identification of the organism.

Step 1: Evaluate each statement individually.
Statement I: Flagellates exhibit gliding locomotion with the help of their flagellae
This is incorrect. Gliding locomotion is typically observed in organisms like sporozoans, not flagellates. Flagellates use their flagella for locomotion but do not exhibit gliding movement. Statement II: Multiple fission in \textit{Amoeba} is called sporulation
This is correct. Sporulation is a process of asexual reproduction where multiple daughter cells are formed inside a cyst during unfavorable conditions. Statement III: Syngamy in \textit{Plasmodium} is hologamy type
This is incorrect. Hologamy refers to a condition where whole organisms act as gametes. In \textit{Plasmodium}, syngamy involves distinct gametes — it is not hologamy. Statement IV: Fusion of pronuclei of gametes is called amphimixis
This is correct. Amphimixis is the process of true sexual reproduction involving the fusion of male and female pronuclei. Conclusion: The correct statements are (2) II, IV.

To identify the bacterium that converts nitrites into nitrates, let’s examine the role of each bacterium in the nitrogen cycle. The process of converting nitrites (NO₂⁻) to nitrates (NO₃⁻) is called nitrification, specifically the second step of nitrification. Nitrobacter is known for this role, as it oxidizes nitrites into nitrates in soil, aiding plant nutrient absorption. Pseudomonas is typically involved in denitrification, reducing nitrates to nitrogen gas, not the conversion of nitrites to nitrates. Nitrosococcus converts ammonia to nitrites, which is the first step of nitrification, not the second. Thiobacillus is known for sulfur oxidation, unrelated to nitrite-to-nitrate conversion.
Final Answer: The bacterium that converts nitrites into nitrates is Nitrobacter, so the correct option is (2).