Bacteria Honor

Nature Study

Requirements

1. What are the main characteristics of a bacterium that place it in a separate kingdom from other living beings?

   Answer: Bacteria are prokaryotes (without a defined nucleus), unicellular, with a peptidoglycan wall, a single circular chromosome, reproducing by binary fission. Kingdom Monera/Bacteria. — The Bacteria kingdom is separated from Animal/Plant/Fungi/Protista by the absence of a nuclear membrane (prokaryotes vs eukaryotes). DNA free in the cytoplasm. A unique peptidoglycan wall. No mitochondria or reticulum. Asexual reproduction by simple division. The 5 classic kingdoms: Monera, Protista, Fungi, Plantae, Animalia (Whittaker 1969).

2. Through drawings or figures, identify the main structures of a bacterial cell.

   Answer: Structures: membrane, cell wall (peptidoglycan), cytoplasm, ribosomes, chromosome (circular DNA), pili, flagellum, capsule. Draw or paste figures identifying them. — The plasma membrane controls entry/exit. The cell wall (rigid, peptidoglycan) protects. 70S ribosomes (smaller than eukaryotic 80S) synthesize proteins. A single circular chromosome floats in the cytoplasm (nucleoid). Pili (short appendages) help adhesion. The flagellum provides movement. The capsule (in some bacteria) protects against the human host's phagocytes.

3. Diagram the 4 main shapes of bacteria.

   Answer: 4 shapes: cocci (spherical, e.g. staphylococci), bacilli (rod, e.g. coli), spirilla (spiral), vibrios (comma, e.g. cholera). Draw each one diagrammed. — Shape is a classic morphological criterion. Cocci can appear isolated (mono), in pairs (diplo), in a chain (strepto), or in a cluster (staphylo). Bacilli are the most common. Spirilla have a polar flagellum. The vibrio Vibrio cholerae causes cholera. An optical microscope (1000x) reveals the shape. Morphological identification is the first step in the microbiology laboratory.

4. What are gram-negative and gram-positive bacteria?

   Answer: Gram-positive: thick peptidoglycan wall (purple color). Gram-negative: thin wall + outer membrane (pink color). The difference is seen by Gram staining in the laboratory. — Gram staining (Christian Gram, 1884) is a key laboratory test in microbiology. Crystal violet stains them all; iodine fixes it in Gram+. Alcohol decolorizes Gram-. Safranin (pink) stains the Gram-. Gram+ (staphylococci, streptococci) — beta-lactam antibiotics are effective. Gram- (E. coli, salmonella) — more resistant to antibiotics due to the outer membrane.

5. Explain the forms of bacterial reproduction. What are the main environmental conditions for a bacterium to reproduce?

   Answer: Reproduction: binary fission (simple, asexual division). Exchanges: conjugation, transformation, transduction. Conditions: temperature, moisture, nutrients, suitable pH. — Binary fission is simple division every 20-30 min in ideal conditions — one bacterium generates 4 million in 7h. Conjugation exchanges DNA via pili. Transformation absorbs free DNA. Transduction uses a virus (bacteriophage) as a vector. Ideal conditions: 35-37°C (the human body), high moisture, available glucose, neutral pH 7. Each species has a preferred niche.

6. How does the feeding and respiration of bacteria occur?

   Answer: Feeding: heterotrophic (consumes) or autotrophic (produces). Respiration: aerobic (uses O2), anaerobic (without O2), or facultative (both). Each bacterium has its own metabolism. — Heterotrophs (90%) consume organic matter from living/dead beings. Autotrophs (cyanobacteria) perform photosynthesis. Strict aerobes depend on O2 (Mycobacterium). Strict anaerobes die with O2 (Clostridium). Facultative ones like E. coli use both. A bacterium absorbs nutrients through its wall and expels waste. Metabolism varies.

7. Cite 3 bacteria that can cause harm to humans. Explain why.

   Answer: 1) Salmonella (food poisoning). 2) Mycobacterium tuberculosis (tuberculosis). 3) Vibrio cholerae (cholera). Each one causes serious disease through toxins or invasion. — Salmonella contaminates raw egg/chicken — acute diarrhea. Mycobacterium tuberculosis attacks the lung (BCG is the vaccine). Vibrio cholerae causes severe diarrhea through a toxin (epidemics in areas without sanitation). Others: pathogenic E. coli, Streptococcus, Helicobacter (ulcer). Treatment with specific antibiotics. Brazil has high vaccination coverage.

8. Cite 3 bacteria beneficial to humans. Explain why.

   Answer: 1) Lactobacillus (yogurt/probiotic). 2) Intestinal E. coli (vitamin K/digestion). 3) Rhizobium (fixes N2 in roots). They help health, nutrition, and agriculture. — Lactobacillus ferments lactose producing yogurt/cheese (Yakult). Harmless E. coli synthesizes vitamin K and protects the intestine. Rhizobium in bean roots converts atmospheric N2 into a plant nutrient. Others: Bifidobacterium (probiotic), soil bacteria decomposing organic matter. The human microbiome has trillions of bacteria essential for health.

9. Cite 1 Bible story that presents a bacterial disease.

   Answer: Naaman's leprosy (2 Kings 5): a Syrian general with leprosy (Mycobacterium leprae) was cured by dipping 7 times in the Jordan River, obeying the prophet Elisha. Today leprosy (Hansen's disease) has a cure. — Biblical leprosy = modern Hansen's disease, caused by Mycobacterium leprae. Naaman (an Aramean general) demonstrates faith and obedience. Other stories: the 10 lepers cured by Jesus (Luke 17), Lazarus the beggar covered in sores (Luke 16), the plague of the Egyptians. Today Hansen's disease has a cure with multidrug therapy (MDT) free through the SUS in Brazil in 6-12 months of treatment.

10. Cite 5 bacterial diseases and some precautions we must take to avoid them.

    Answer: Tuberculosis (BCG vaccine). Salmonella (cook well). Cholera (potable water). Tetanus (vaccine/dressing). Syphilis (condom). Hygiene + vaccination + sanitation. — Tuberculosis through the air — BCG vaccine at birth. Salmonella in raw egg/chicken — cook above 70°C. Cholera through contaminated water — drink it filtered/boiled. Tetanus through a dirty wound — vaccine and cleaning. Syphilis through sex — use of a condom. Others: diphtheria (vaccine), pneumonia, meningitis. The SUS offers all vaccines free in modern Brazil.

11. What is the importance of not using antimicrobials without a medical prescription?

    Answer: Without a prescription: it creates bacterial resistance, kills the good intestinal flora, masks symptoms of serious disease, and poisons the liver/kidney. A doctor evaluates and indicates the correct antibiotic. — Bacterial resistance is a worldwide problem — superbugs (KPC, MRSA) no longer respond to antibiotics. The WHO predicts 10 million deaths per year by 2050. Anvisa requires a controlled prescription for antibiotics in Brazil since 2010. Incomplete doses select for resistance. Each antibiotic acts on a specific bacterium. The doctor identifies the right bacterium via culture+antibiogram.