Microbiology Study Guide: Eukaryotes, Viruses, Classification, and Metabolism

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Kingdom Protista: Fungi, Algae, and Protozoa

Fungal Spores vs. Bacterial Endospores

Fungal spores and bacterial endospores are both reproductive or survival structures, but they differ significantly in function and formation.

Fungal Spores: Produced for reproduction; can be sexual or asexual; generally less resistant to harsh conditions.
Bacterial Endospores: Survival structures; highly resistant to heat, desiccation, and chemicals; not for reproduction.
Example: Bacillus species form endospores, while Aspergillus forms conidiospores.

Types of Fungal Spores

Fungi produce various types of asexual spores for reproduction.

Conidiospores: Non-enclosed spores formed on conidiophores.
Arthroconidium: Fragmented hyphae acting as spores.
Blastoconidium: Budding spores from parent cells.
Chlamydoconidium: Thick-walled spores formed within hyphae.
Sporangiospores: Enclosed in a sporangium.

Sexual Spore Formation in Fungi

Sexual reproduction in fungi involves three stages:

Plasmogamy: Fusion of cytoplasm from two parent cells.
Karyogamy: Fusion of nuclei from the fused cells.
Meiosis: Reduction division to produce haploid spores.

Major Characteristics and Habitat of Algae

Algae are photosynthetic eukaryotes found in aquatic environments.

Habitat: Mostly aquatic; water provides support, nutrients, and dispersal.
Benefits: Water allows for efficient photosynthesis and nutrient uptake.

Algal Reproduction

Unicellular Algae: Reproduce by mitosis.
Multicellular Algae: Reproduce by fragmentation or sexual reproduction.

Vegetative Structures of Algae

Algae have specialized structures for support and photosynthesis.

Thallus: The body of seaweeds.
Holdfast: Anchors the algae to a substrate.
Stipes: Stem-like structures.
Blades: Leaf-like structures for photosynthesis.

Comparison: Multicellular Algae vs. Plants

Algae: Lack true roots, stems, and leaves; have simpler structures.
Plants: Possess complex tissues and organs.

Four Major Phyla of Algae

Brown Algae (Kelp): Contains algin, a polysaccharide used in food and industry.
Red Algae: Found in deep ocean due to pigment adaptation; produces agar; generally non-toxic.
Green Algae: Cell walls made of cellulose; produce chlorophylls; similar to plant cells.
Euglenoids: Have a pellicle, red eyespot for light detection, and flagellum for movement.

Superclades: Stramenopila and Alveolata

Diatoms: Silica cell walls; store energy as oils; produce domoic acid (a toxin).
Water Molds: Decomposers; some produce toxins; caused Ireland’s potato famine.
Dinoflagellates: Important plankton; have cellulose in membranes; some produce toxins.

General Characteristics of Protozoans

Protozoans are unicellular eukaryotes with diverse modes of nutrition and reproduction.

Trophozoite: Active, feeding stage.
Encystment: Formation of a cyst for protection.
Cyst: Dormant, resistant stage.

Protozoan Reproduction

Asexual: Binary fission, budding, schizogony (multiple fission).
Sexual: Conjugation.

Hosts in Protozoan Life Cycles

Intermediate Host: Harbors immature or asexual stage.
Definitive Host: Harbors mature or sexual stage.

Protozoan Nutrition

Aerobic Heterotrophs: Require oxygen and organic nutrients.
Pellicle: Flexible outer covering.
Cytostome: Cell mouth for ingestion.
Pseudopods: Extensions for movement and phagocytosis.

Medically Important Protozoa

Excavata: Includes Giardia intestinalis (lacks mitochondria) and Trichomonas vaginalis.
Euglenozoa: Includes hemoflagellates like Trypanosoma brucei and Trypanosoma cruzi.
Amoebozoa: Use pseudopods; Entamoeba histolytica causes disease.
Apicomplexa: Obligate parasites; Plasmodium causes malaria; Toxoplasma gondii requires multiple hosts and is dangerous for pregnant people.
Ciliates: Have cilia for movement and feeding; Balantidium coli causes disease.

Kingdom Protista: Helminths

Definition and Characteristics of Helminths

Helminths are multicellular parasitic worms with complex life cycles.

Multicellular: Unlike protozoa, helminths are composed of many cells.
Life Cycle: Includes egg, larva, and adult stages.
Organ Systems: Digestive, nervous, reproductive, and excretory systems.
Features: Adaptations for parasitism, such as cuticle, suckers, and reproductive capacity.

Dioecious vs. Monoecious Helminths

Dioecious: Separate male and female individuals.
Monoecious: Both sexes in one organism (hermaphroditic).

Hosts in Helminth Life Cycles

Intermediate Host: Harbors larval stage.
Definitive Host: Harbors adult, sexually mature stage.

Major Phyla of Parasitic Worms

Platyhelminthes (Flatworms):
- Trematodes (Flukes): Oral sucker for attachment; cuticle for protection.
- Cestodes (Tapeworms): Found in intestines; scolex for attachment; proglottids for reproduction.
- Examples: Taenia saginata (definitive host: human); Echinococcus granulosus (intermediate host: human, dead-end).
Nematoda (Roundworms):
- Sexual Dimorphism: Males and females differ in size/shape.
- Eggs Infective: Ascaris lumbricoides, Enterobius vermicularis.
- Larvae Infective: Necator americanus, Ancylostoma duodenale, Dirofilaria immitis (heartworms; affects dogs; mosquito vector).

Viruses, Viroids, and Prions

Comparison: Viruses vs. Bacteria

Viruses: Non-living, require host for replication, smaller than bacteria.
Bacteria: Living cells, can reproduce independently.

Distinctive Characteristics of Viruses

Obligate intracellular parasites
Contain nucleic acid (DNA or RNA)
Protein coat (capsid)
Some have envelopes

Viral Size Range

20–300 nm; much smaller than bacteria and eukaryotic cells.

Host Range and Infection Factors

Host Range: Specific species or cell types a virus can infect.
Factors: Attachment ability, presence of cellular factors.

Virus vs. Virion

Virus: General term for the infectious agent.
Virion: Complete, infectious viral particle.

Major Viral Structures

Nucleic Acids: DNA or RNA, single or double-stranded.
Capsid: Protein coat; made of capsomeres; protects genome.
Envelope: Lipid membrane; contains spikes for attachment.
Non-enveloped Viruses: Lack envelope; often more resistant.

Types of Viruses by Morphology

Helical
Polyhedral
Complex
Enveloped

Viral Multiplication

One-step Growth Curve: Describes viral replication.
Eclipse Period: Time when no infectious virions are detected.
Virion Yield: One virion can produce hundreds of progeny.
Host Cell Outcome: Cell lysis or persistent infection.

Bacteriophage Multiplication: Lytic and Lysogenic Cycles

Lytic Cycle: Attachment, penetration, biosynthesis, maturation, release; results in cell lysis.
Lysogenic Cycle: Viral genome integrates as prophage; cell survives; can later enter lytic cycle.
Definitions: Prophage (integrated viral DNA), lysogeny (state of integration), lysogenic cells (carry prophage).
Trigger: Environmental stress can induce lytic cycle.

Animal Virus Multiplication

Similar steps as bacteriophage, but includes uncoating (unique to animal viruses).
Differences in entry, uncoating, and release mechanisms.

Viroids, Virusoids, and Prions

Viroid: Infectious RNA, affects plants.
Virusoid: Infectious RNA, requires helper virus, affects plants.
Prion: Infectious protein, affects animal nervous tissue; causes neurodegenerative diseases.

Classification and Identification of Microorganisms

Classification vs. Identification

Classification: Grouping organisms based on shared characteristics.
Identification: Determining the specific organism present.

Medical Microbiology

Study of microorganisms causing disease in humans.

Bergey’s Manual: Properties for ID and Classification

Cell morphology
Staining characteristics
Biochemical properties
Source and habitat

Conventional Identification Methods

Differential Staining: Gram stain, acid-fast stain.
Biochemical Testing: Enzyme activity, metabolic products.
Rapid Identification: Multiple tests in one system.

Serology and Serological Methods

Serology: Study of serum and immune responses.
Serum: Fluid portion of blood.
Antigens: Molecules that elicit immune response.
Antibodies: Proteins that bind antigens.
Antiserum: Serum containing antibodies.

Serological Identification Methods

Slide agglutination test
ELISA (Enzyme-Linked Immunosorbent Assay)
Western blotting

Phage Typing

Bacteriophage: Virus that infects bacteria.
Phage Typing: Using phages to identify bacterial strains.

Microbial Metabolism

Definition and Key Players

Metabolism: All chemical reactions in a cell.
Enzymes: Biological catalysts.
ATP: Main energy currency.

Enzymes and Chemical Reactions

Substrate: Molecule acted upon by enzyme.
Product: Result of enzymatic reaction.
Cofactors: Non-protein helpers (metal ions, electron carriers).

ATP Structure and Function

Adenosine (adenine + ribose)
Three phosphate groups
Energy released by breaking terminal phosphate bond

Metabolic Pathways

Catabolism: Breakdown of molecules; hydrolytic, exergonic.
Anabolism: Synthesis of molecules; dehydration, endergonic.
Pathways are complex and interconnected.

Coupled Reactions

Catabolic reactions provide energy for anabolic reactions.
ATP synthesis is coupled to catabolism; ATP breakdown is coupled to anabolism.

Enzymes and Energy Production

Catalysts: Speed up reactions without being consumed.
Enzymes: Protein catalysts.
Ribozymes: RNA catalysts.
Apoenzyme: Protein part of enzyme.
Holoenzyme: Apoenzyme + cofactor.
Active Site: Where substrate binds.
Allosteric Site: Regulatory site.

Enzyme Regulation

Optimal temperature and pH required.
High substrate concentration increases activity.
Inhibitors: Competitive (bind active site), noncompetitive (bind allosteric site).
Feedback inhibition regulates pathways.

Oxidation-Reduction Reactions

Oxidation: Loss of electrons.
Reduction: Gain of electrons.
Always occur together (redox).
Dehydrogenation: Removal of hydrogen atoms.

ATP Production: Phosphorylation

Substrate-level phosphorylation: Direct transfer of phosphate.
Oxidative phosphorylation: Electron transport chain and chemiosmosis.
Photophosphorylation: Light-driven, in photosynthesis.

Carbohydrate Catabolism: Cellular Respiration

Definition and Major Processes

Carbohydrate Catabolism: Breakdown of sugars for energy.
ATP produced by glycolysis and cellular respiration.

Cellular Respiration Types

Aerobic: Uses oxygen as terminal electron acceptor.
Anaerobic: Uses other molecules (nitrate, sulfate).

Stages of Cellular Respiration

Glycolysis
Krebs Cycle
Electron Transport Chain (ETC)

Glycolysis

Occurs in cytoplasm.
Two stages: energy investment and energy payoff.
Net ATP: 2 per glucose.
End-product: pyruvic acid.

Alternative Pathways

Pentose phosphate pathway
Entner-Doudoroff pathway

Preparatory Step: Pyruvic Acid

Converts pyruvic acid to acetyl-CoA.
Occurs in mitochondria (eukaryotes) or cytoplasm (prokaryotes).
Produces NADH and CO2.

Krebs Cycle

Main molecule: acetyl-CoA.
Two turns per glucose.
Reactions: oxidation, decarboxylation, substrate-level phosphorylation.
Products: CO2, NADH, FADH2, ATP.
Location: mitochondria (eukaryotes), cytoplasm (prokaryotes).

Electron Transport Chain (ETC)

NADH and FADH2 donate electrons.
NADH enters at complex I; FADH2 enters later.
H+ pumped across membrane, creating electrochemical gradient.
Chemiosmosis: ATP synthesis driven by gradient.
ATP Synthase: Enzyme catalyzing ATP formation.

ATP Yield

10 NADH: 30 ATP
2 FADH2: 4 ATP
Prokaryotes: 38 ATP per glucose
Eukaryotes: 36 ATP per glucose (due to transport costs)

Terminal Electron Acceptors

Aerobic: Oxygen
Anaerobic: Nitrate, sulfate, etc.
Anaerobes grow slower due to less efficient ATP production.

Fermentation

Definition and Major Points

Occurs without oxygen.
ATP produced only in glycolysis.
Energy remains in end-products.

Advantages and End-Products

Allows survival in anaerobic conditions.
End-products depend on organism, substrate, and enzymes.

Homolactic vs. Heterolactic Fermentation

Homolactic: Produces only lactic acid.
Heterolactic: Produces lactic acid and other products.

Lactic and Ethanol Fermentation

Lactic fermentation: Pyruvate to lactic acid.
Ethanol fermentation: Pyruvate to ethanol and CO2.

Catabolism of Lipids and Proteins

Lipid Catabolism

Fats: Composed of glycerol and fatty acids.
Lipases: Enzymes that break down lipids.
Glycerol enters glycolysis; fatty acids enter Krebs cycle after modification.

Protein Catabolism

Proteins: Polymers of amino acids.
Amino Acids: Central carbon, amino group, carboxyl group, R group.
Proteases/Peptidases: Enzymes that break down proteins.
Modifications before entering Krebs cycle: deamination, decarboxylation, desulfurization.
Modified amino acids feed into glycolysis, Krebs cycle, or ETC.

Process	Main Substrate	ATP Yield	Location (Eukaryotes)
Glycolysis	Glucose	2 ATP	Cytoplasm
Krebs Cycle	Acetyl-CoA	2 ATP	Mitochondria
ETC	NADH/FADH2	32-34 ATP	Mitochondria
Fermentation	Pyruvate	2 ATP	Cytoplasm

Additional info: Some details were inferred for completeness, such as the ATP yield table and expanded explanations of metabolic pathways.