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:

1. Plasmogamy: Fusion of cytoplasm from two parent cells.

2. Karyogamy: Fusion of nuclei from the fused cells.

3. 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

1. Glycolysis

2. Krebs Cycle

3. 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.

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