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Questions and Answers
Which structure is commonly associated with typical eukaryotic cells?
What type of ribosomes are found in eukaryotic cells?
What is the main method of reproduction for unicellular fungi?
Which of the following fungi can switch between two forms due to environmental stimulus?
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Which of the following protozoa are known as 'hunters' and 'grazers'?
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What type of cell walls do protozoa lack?
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What type of cell division do some protozoa undergo for asexual reproduction where the nucleus divides multiple times before the cell divides?
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Which factor triggers the switch from mycelial to yeast-like form in some fungi?
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What term describes the reproductive structures formed by multicellular fungi?
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Which of the following is NOT a characteristic of eukaryotes?
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Which characteristic is unique to Archaea compared to Bacteria?
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Which of the following shapes is NOT typically associated with bacteria?
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What is a defining feature of methanogens among archaea?
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How do bacteria primarily reproduce?
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Which of the following statements about archaeal cell walls is true?
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What is a notable feature of the ribosomes found in bacteria and archaea?
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What distinguishes fungi in terms of their nutritional mode?
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Which of the following accurately describes the composition of archaeal membranes?
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Why are archaea considered a distinct grouping from bacteria?
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Study Notes
Microbial Diversity
- Microorganisms come in all different shapes and sizes.
- The diversity seen is a result of 3.8 billion years of evolution.
Bacteria
- The most abundant group of “living” organisms on Earth.
- Relatively simple, unicellular (chains, clusters), prokaryotic with no organelle structure.
- Usually 1, circular chromosome (haploid), some contain plasmids.
- DNA is not associated with histones, genes contain no introns.
- Many bacteria swim (flagella).
- Divide by binary fission, exponential growth.
- Characteristic 70S ribosomes.
- Several shapes reported: cocci, bacilli, spirilla.
- Individual bacteria may form pairs, chains and clusters.
Archaea
- Live in extreme environments (methanogens, extreme halophiles, extreme thermophiles).
- Predominantly chemoautotrophs.
- Share many properties with bacteria (unicellular, prokaryotes, no organelle structure).
- Divide by binary fission, usually 1, circular chromosome, genes contain no introns.
- Originally classified with bacteria (Prokaryotes).
- Woese & Fox (1977) proposed that Archaea were distinct grouping.
- 70S Ribosomes unique to the Archaea.
- DNA associated with histones (eukaryotic-like).
- Enclosed by a plasma membrane and rigid cell wall.
- Cell walls lack peptidoglycan: some have “S-layer”, some have pseudopeptidoglycan.
- Membranes composed of branched hydrocarbon chains attached to glycerol by ether linkages (R-O-R), different to bacteria.
Fungi
- Chemoheterotrophs: degrade complex carbon chains (lignin, cellulose) to produce energy.
- Typical eukaryotes features (membrane bound organelles, multiple linear chromosomes, some haploid, some diploid, genes contain introns & exons, DNA associated with histones, 80S ribosomes).
- Rigid cell wall containing chitin.
Unicellular Fungi
- Bakers, brewers & fission yeast, Candida albicans.
- Generally oval shaped, much larger than bacteria.
- Yeast budding (asexual): buds form and pinch off of the parent cell.
- Yeast can form spores (sexual).
Multicellular Fungi
- Form mycelia: Long branched filaments called vegetative hyphae.
- Reproduction via spores.
- Hyphal fragmentation (asexual).
- Sporangia (asexual).
- Gametangia (sexual).
Dimorphic Fungi
- Grow either unicellular (yeast) or as mycelium (mold).
- Switch can be an environmental stimulus.
- Blastomyces dermatitidis: survives in soil that contains organic debris, infects mammals.
- Mycelium, switch at 37°C triggers change to yeast-like form, causes Blastomycosis.
Protozoa
- Predominantly chemoheterotrophs - “hunters” and “grazers,” feed on other microbes.
- Free living (Paramecium, Amoeba), parasitic (Plasmodium, Trypanosoma, Giardia).
- Unicellular.
- Typical eukaryotes features (membrane bound organelles, multiple linear chromosomes, DNA associated with histones eukaryotes, genes contain introns & exons, 80S ribosomes).
- Lack cell walls.
- They move by pseudopodia, flagella, cilia.
Protozoa Reproduction
- Asexual reproduction: Binary fission, schizogony, budding.
- Some protozoa reproduce sexually by fusion of gametes.
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Description
Explore the fascinating world of microorganisms, focusing on their diversity resulting from billions of years of evolution. This quiz delves into the characteristics of bacteria and archaea, their structures, and their roles in various environments. Test your knowledge on these fundamental life forms and their unique features.
