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Questions and Answers
What is the main method of asexual reproduction in bacteria?
Which bacteria are known for their ability to fix atmospheric nitrogen in symbiotic relationships?
What process involves the uptake of DNA from the surrounding environment by bacterial cells?
What condition do bacteria not face during population increase that leads to stopping replication?
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What is the primary function of mesosomes during binary fission?
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Which type of bacteria is known for living in extreme environments?
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Which of the following is NOT a method of genetic recombination in bacteria?
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What role do methanogens play in ecosystems?
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What environment do halophiles typically inhabit?
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Which characteristic defines thermoacidophiles?
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What is the primary role of heterocysts in cyanobacteria?
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Which of the following is NOT a method of asexual reproduction in bacteria?
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Which cyanobacterium is noted for causing algal blooms?
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What is the main habitat of cyanobacteria?
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What is an example of a eubacterium involved in biological nitrogen fixation?
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Which structure do filamentous cyanobacteria use for reproduction?
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Which type of respiration can facultative anaerobes perform?
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What shape is associated with the bacterium Bacillus subtilis?
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Which type of bacteria utilizes non-sulfur aliphatic organic compounds as electron donors?
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What is the primary energy source used by chemosynthetic autotrophic bacteria?
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Which of the following examples belongs to photosynthetic autotrophic bacteria?
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What type of bacteria can only survive in the absence of oxygen?
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Which pigments are involved in the process of bacterial photosynthesis?
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Which type of bacteria is most abundant in nature and primarily serves as decomposers?
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What is the primary component of the cell wall in hyphae?
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Which type of spore is produced endogenously in a sporangium?
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Which of the following is NOT a method of vegetative reproduction in fungi?
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What characteristic distinguishes oospores from ascospores?
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In sexual reproduction, what is the resting phase after plasmogamy called?
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Which of the following spores is formed under unfavorable conditions?
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Which gametic fusion method involves the direct fusion of two gametes?
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What is the primary function of the fungal reserve food sources like oil and glycogen?
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What distinguishes euglenoids from other protists?
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Which type of reproduction can slime moulds perform?
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Which organism is primarily responsible for causing malaria?
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What is the nutritional mode of euglenoids?
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What type of spores do slime moulds produce when under unfavourable conditions?
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What is the primary function of the stigma in euglenoids?
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Which of the following describes the habitat of fungi?
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What is the network of filaments that make up the body of fungi called?
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Study Notes
Bacteria: Morphology & Nutrition
- Bacteria exhibit diverse shapes:
- Coccus: Spherical (e.g., Micrococcus)
- Bacillus: Rod-shaped (e.g., Lactobacillus)
- Vibrio: Comma-shaped (e.g., Vibrio cholerae)
- Spirillum: Spiral-shaped (e.g., Pseudomonas)
Bacteria: Respiration
- Bacteria can engage in both aerobic and anaerobic respiration:
- Obligate/strict aerobes: Require oxygen for survival (e.g., Bacillus subtilis)
- Obligate/strict anaerobes: Cannot survive in the presence of oxygen (e.g., Clostridium botulinum)
- Facultative aerobes: Can respire both aerobically and anaerobically (e.g., Chlorobium)
- Facultative anaerobes: Typically respire aerobically but can switch to anaerobic respiration when oxygen is limited (e.g., Pseudomonas)
Bacteria: Autotrophic Nutrition
- Autotrophic bacteria obtain carbon from inorganic sources:
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Photosynthetic autotrophic bacteria:
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Photo-lithotrophic bacteria: Utilize light energy for food synthesis, containing pigments like bacteriochlorophyll, bacteriopurpurin, and bacterioviridin.
- Purple sulfur bacteria: Contain bacteriopurpurin and utilize inorganic sulfur compounds (H₂S, thiosulfate) as electron and H+ donors (e.g., Thiospirillum, Chromatium).
- Green sulfur bacteria: Contain bacterioviridin and use H₂S as electron and H+ donors (e.g., Chlorobium limicola).
- Water is not the electron source in bacterial photosynthesis, making it anoxygenic.
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Photo-organotroph:
- Purple non-sulfur bacteria: Use non-sulfur aliphatic organic compounds as electron and H+ donors (e.g., Rhodospirillum).
- Green non-sulfur bacteria: Also use non-sulfur aliphatic organic compounds (e.g., Chloronema).
- Most photosynthetic bacteria are anaerobes (facultative aerobes).
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Photo-lithotrophic bacteria: Utilize light energy for food synthesis, containing pigments like bacteriochlorophyll, bacteriopurpurin, and bacterioviridin.
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Chemosynthetic autotrophic bacteria: Obtain energy by oxidizing inorganic substances, playing a vital role in nutrient recycling.
- Nitrifying bacteria: Convert ammonia (NH₃) to nitrogen (N₂) (e.g., Nitrosomonas, Nitrococcus).
- Iron bacteria: Utilize iron as an energy source (e.g., Ferrobacillus, Leptothrix).
- Hydrogen bacteria: Utilize hydrogen gas (e.g., Hydrogenomonas).
- Sulfur bacteria: Oxidize sulfur compounds (e.g., Beggiatoa, Thiobacillus thioxidans).
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Photosynthetic autotrophic bacteria:
Bacteria: Heterotrophic Nutrition
- Heterotrophic bacteria obtain carbon from organic compounds, being the most abundant bacteria in nature.
- Saprophytes: Decompose dead organic matter (e.g., Bacillus subtilis).
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Symbiotic: Many are gram-negative and capable of fixing atmospheric nitrogen.
- Rhizobium: Associated with legume roots.
- Azatobactor, Klebsiella, Beijerinckia: Aerobic nitrogen fixers.
- Clostridium: Anaerobic nitrogen fixer.
- Parasitic: Obtain nutrients from living organisms (plants or animals).
Bacteria: Reproduction
- Reproduction is primarily asexual but can involve genetic recombination:
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Asexual Reproduction:
- Binary fission: Most common method, involves cell division into two daughter cells.
- Endospore formation: Occurs under unfavorable conditions, forming resistant spores containing calcium dipicolinic acid.
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Sexual/genetic recombination:
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Transformation: Genetic recombination without direct contact between bacterial cells.
- Discovered by Griffith, utilizing Diplococcus and Streptococcus pneumoniae.
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Conjugation: Requires direct contact between bacterial cells.
- Discovered by Lederberg and Tatum, utilizing E. coli.
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Transduction: Genetic recombination mediated by bacteriophages.
- Discovered by Zinder and Lederberg, utilizing Salmonella typhimurium.
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Transformation: Genetic recombination without direct contact between bacterial cells.
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Asexual Reproduction:
Bacteria: Types
- Bacteria are classified into two major groups:
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Archaebacteria: Primitive bacteria with unique cell wall structure and branched chain lipids, allowing survival in extreme environments.
- Methanogens: Produce methane in marshy habitats and ruminant guts (e.g., Methanococcus, Methanobacterium).
- Halophiles: Thrive in high-salt environments (e.g., Halobacterium, Halococcus).
- Thermoacidophiles: Tolerate high temperatures and low pH, typically found in hot springs (e.g., Thermoplasma, Thermoproteus).
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Eubacteria/True bacteria:
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Cyanobacteria: Gram-negative photosynthetic prokaryotes, responsible for oxygenic photosynthesis and atmospheric oxygen enrichment.
- Blue-green algae: Classified under Cyanophyceae and Myxophyceae.
- Anabaena azollae: Found in association with Azolla.
- Anabaena cycadae: Associated with the coralloid roots of Cycas.
- Cyanelle: Cyanobacteria living endozoically in protozoans.
- Lack flagella throughout their life cycle.
- Trichodesmium erythrium imparts a red color to the sea.
- Nitrogen fixation occurs anaerobically in heterocysts by the nitrogenase enzyme.
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Mycoplasma: Lack cell walls, found in soil, sewage, and infect both plants and animals.
- Discovered by Nocard and Roux from cattle pleural fluid.
- Classified under the genus Mycoplasma.
- Noctiluca: Bioluminescent dinoflagellate, known as night light or fire algae.
- Gonyaulax: Produces saxitoxin, causing paralytic shellfish poisoning (PSP).
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Cyanobacteria: Gram-negative photosynthetic prokaryotes, responsible for oxygenic photosynthesis and atmospheric oxygen enrichment.
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Archaebacteria: Primitive bacteria with unique cell wall structure and branched chain lipids, allowing survival in extreme environments.
Other Protists
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Euglenoids: Unicellular, flagellated protists with a flexible pellicle instead of a cell wall.
- Have two flagella: one long and one reduced.
- Contain photosensitive paraflagellar body.
- Perform metaboly (creeping movement) using myonemes.
- Stigma (eyespot) contains astaxanthin pigment for light sensing.
- Exhibit both photoautotrophic and mixotrophic nutrition.
- Store reserve food as paramylon.
- Form palmella stage and cysts for perennation under unfavorable conditions.
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Slime moulds: Free-living organisms that creep over damp surfaces, forming plasmodia under favorable conditions.
- Have naked protoplast.
- Form fruiting bodies under unfavorable conditions, releasing resistant spores.
- Exhibits both asexual and sexual reproduction.
- Form a connection between plants, animals, and fungi.
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Protozoans: Unicellular eukaryotic organisms, classified based on their mode of locomotion:
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Amoeboid: Move using pseudopodia.
- Entamoeba histolytica: Causes dysentery.
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Flagellated: Move using flagella.
- Trypanosoma paladium: Causes sleeping sickness.
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Ciliated: Move using cilia.
- Paramecium: A common ciliate.
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Sporozoans: Lack locomotory structures.
- Plasmodium: Causes malaria.
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Amoeboid: Move using pseudopodia.
Fungi
- Cosmopolitan: Found in various environments, particularly warm and humid areas.
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Forms: Exhibit diverse forms:
- Corticolous: Grow on bark.
- Coprophilous: Grow on cow dung.
- Epixylic: Grow on wood.
- Xylophilous: Grow on burnt wood.
- Keratinophilous: Grow on keratin.
- Multicellular: Except yeasts and Synchytrium.
- Fungal body (mycelium): Composed of hyphae.
- Hyphae: Filamentous structures with cell walls of chitin or fungal cellulose.
- Reserve food: Oil and glycogen.
- Heterotrophic nutrition: Obtain nutrients from organic sources.
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Reproduction:
- Vegetative: Fragmentation, fission, budding.
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Asexual: Produces mitospores.
- Zoospores: Uniflagellate or biflagellate (e.g., Synchytrium, Pythium, Saprolegnia).
- Sporangiospores: Thin-walled, non-motile spores produced inside sporangia (e.g., Rhizopus, Mucor).
- Conidia: Thin-walled, non-motile spores produced externally on conidiophores (e.g., Aspergillus, Penicillium).
- Chlamydospores: Thick-walled, resting spores formed under unfavorable conditions (e.g., Rhizopus).
- Oidia: Thin-walled spores produced under sugar-rich conditions (e.g., Rhizopus).
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Sexual:
- Occurs through oospores, ascospores, and basidiospores produced in fruiting bodies.
- Involves plasmogamy (cytoplasm fusion), karyogamy (nucleus fusion), and meiosis.
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Plasmogamy can occur through:
- Planogametic copulation: Fusion of two gametes of opposite sex (e.g., Allomyces).
- Gametangial contact: Two gametangia touch, but the gametes do not fuse (e.g., Pythium, Albugo).
- Gametangial copulation: Direct fusion of gametangia (e.g., Mucor, Rhizopus).
- Spermatization: Spermatia transferred to female hyphae (e.g., Puccinia).
- Somatogamy: Direct fusion of hyphae (e.g., Agaricus).
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Test your knowledge on bacterial morphology, nutrition, and respiration. This quiz covers various shapes of bacteria, types of respiration, and mechanisms of autotrophic nutrition. Perfect for biology students seeking to reinforce their learning.
