Comprehensive Study Guide for Microbiology: Cells, Growth, Metabolism, and Microbial Control

Chapter 1: The Invisible World

Major Groups of Microorganisms

This section covers the seven major groups of microorganisms, their cellular organization, reproduction, motility, and unique features.

Microbe Type	Eukaryotic/Prokaryotic/Acellular	Unicellular/Multicellular/Other	Asexual/Sexual Reproduction	Organelles/Non-membrane organelles	Non-motile/Motile	Cell envelope	Unique Features
Bacteria	Prokaryotic	Unicellular	Asexual (binary fission)	No membrane-bound organelles	Motile or non-motile (flagella)	Peptidoglycan cell wall	Ubiquitous, diverse metabolism
Archaea	Prokaryotic	Unicellular	Asexual	No membrane-bound organelles	Motile or non-motile	No peptidoglycan; unique lipids	Extreme environments
Fungi	Eukaryotic	Unicellular (yeasts) or multicellular (molds)	Sexual and asexual	Membrane-bound organelles	Non-motile	Chitin cell wall	Decomposers
Protozoa	Eukaryotic	Unicellular	Sexual and asexual	Membrane-bound organelles	Motile (cilia, flagella, pseudopodia)	No cell wall	Complex life cycles
Algae	Eukaryotic	Unicellular or multicellular	Sexual and asexual	Membrane-bound organelles	Motile or non-motile	Cellulose cell wall	Photosynthetic
Helminths	Eukaryotic	Multicellular	Sexual and asexual	Membrane-bound organelles	Motile (larval stages)	No cell wall	Parasitic worms, eggs
Viruses	Acellular	Neither	Require host for replication	None	Non-motile	Protein coat (capsid), sometimes envelope	Obligate intracellular parasites

Key Definitions and Concepts

• Ubiquitous: Microorganisms are found everywhere in nature.

• Pathogenic: Capable of causing disease; most bacteria, some fungi, protozoa, and viruses are pathogenic. (Disease causing)

• Opportunistic (sometimes) Pathogen: Normally harmless but can cause disease in immunocompromised hosts. ( can cause disease under proper conditions) many bacteria

• Obligate (always) pathogens/parasites cause disease due to their need to persist inside a host (most viruses )

• Microbiome: all of the microbes that live stably in a particular environment (vagina, gut, skin, oral)

• Dysbiosis: is a change in the microbiome or an overgrowth of a specific pathogenic microbes leading to disease

Historical Discoveries

• Antonie van Leeuwenhoek: First to observe living microbes using a microscope.

• Louis Pasteur: Disproved spontaneous generation; developed pasteurization.

• Germ Theory: Diseases are caused by microorganisms (Lister and Koch contributed key findings).

Chapter 4: Cells

Prokaryotic Cell Structure and Function

• Size: Prokaryotic cells are typically 0.2–2.0 μm in diameter.

• Monomorphic vs. Pleomorphic: Monomorphic cells have a single shape; pleomorphic cells can vary in shape.

Cell Components

• Glycocalyx: Gel-like layer outside cell wall; protects and aids in attachment.

• Cell Wall: Provides structure and prevents osmotic lysis; peptidoglycan in bacteria.

• Plasma Membrane: Selectively permeable barrier; site of metabolic processes.

• Pili: Hair-like structures for attachment or DNA transfer (conjugation).

• Flagella: Motility structures; rotate to propel cell.

• Fimbriae: Shorter than pili; used for attachment.

• Cytoplasm: Gel-like substance inside cell membrane.

• Ribosomes (70S): Sites of protein synthesis.

• Nucleoid: Region containing circular DNA.

• Plasmid: Small, circular DNA molecules; often carry antibiotic resistance genes.

• Storage Vacuoles: Store nutrients and waste products.

Peptidoglycan Structure

• Composed of sugar chains (N-acetylglucosamine and N-acetylmuramic acid) cross-linked by peptides.

Cell Envelope

• Includes plasma membrane, cell wall, and sometimes outer membrane (in Gram-negative bacteria).

Gram-Positive vs. Gram-Negative Cell Envelopes

• Gram-Positive: Thick peptidoglycan, teichoic acids, no outer membrane.

• Gram-Negative: Thin peptidoglycan, outer membrane with lipopolysaccharide (LPS), periplasmic space.

Flagella Patterns

Monotrichous & polar	Lophotrichous & polar	Amphitrichous & polar	Peritrichous
Single flagellum at one end	Cluster of flagella at one end	Flagella at both ends	Flagella all over surface

• Flagella Movement: Rotation; can be clockwise (tumble) or counterclockwise (run).

Shared Features of Eukaryotes and Prokaryotes

• Plasma membrane, cytoplasm, ribosomes, genetic material (DNA).

Key Differences

• Eukaryotes have membrane-bound organelles, larger size, and linear chromosomes.

• Prokaryotes lack organelles, are smaller, and have circular DNA.

Chapter 6: Microbial Growth

Macronutrients and Micronutrients

• Macronutrients: Required in large amounts (C, H, O, N, P, S, K, Mg, Ca, Fe).

• Micronutrients: Trace elements (Mn, Zn, Co, Mo, Ni, Cu); regulate enzyme function.

Oxygen Requirements

• Obligate Aerobes: Require oxygen.

• Obligate Anaerobes: Killed by oxygen.

• Facultative Anaerobes: Grow with or without oxygen.

• Microaerophiles: Require low oxygen.

• Aerotolerant Anaerobes: Tolerate oxygen but do not use it.

• Key Enzymes: Catalase and superoxide dismutase detoxify reactive oxygen species.

Temperature and pH Preferences

• Psychrotrophs: Grow at low temperatures.

• Mesophiles: Moderate temperatures (20–45°C).

• Thermophiles: High temperatures.

• Acidophiles: Acidic environments.

• Neutrophiles: Neutral pH.

• Alkaliphiles: Basic environments.

Osmotic Pressure

• Regulates water movement; high salt/sugar inhibits growth by plasmolysis.

Binary Fission

• Cell replicates DNA, elongates, divides into two identical cells.

Endospore Formation

• Occurs in harsh conditions; two stages: sporulation (formation) and germination (return to vegetative state).

• Endospores are highly resistant and dormant; formation is reversible.

Chapter 7: Control of Microbial Growth

Bacterial Death Rate

• Factors: Number of microbes, environment, time of exposure, microbial characteristics.

Physical Sterilization Methods

• Moist Heat: Autoclaving, boiling.

• Dry Heat: Flaming, oven.

• Radiation: Ionizing (gamma rays), non-ionizing (UV).

Germicidal Levels

Level	Microbes Killed
Low	Vegetative bacteria, fungi, some viruses
High	All microbes except high levels of endospores
Sterilant	All forms of microbial life, including endospores

Chemical Agents

• Phenols: Disrupt membranes, denature proteins.

• Halogens (Iodine, Chlorine): Oxidize cell components.

• Alcohols: Denature proteins, dissolve lipids.

• Heavy Metals: Inactivate proteins.

• QUATs: Disrupt membranes.

• Soap: Degerming, not antimicrobial.

Chapter 9: Microbial Metabolism

Anabolism vs. Catabolism

• Anabolism: Biosynthetic reactions; build complex molecules, require energy.

• Catabolism: Breakdown of molecules; release energy.

Microbial Nutrition Types

Nutrition Type	Carbon Source	Energy Source
Photoautotroph	CO2	Light
Chemoautotroph	CO2	Inorganic chemicals
Photoheterotroph	Organic compounds	Light
Chemoheterotroph	Organic compounds	Organic compounds

Enzymes and Enzyme Activity

• Enzymes: Biological catalysts; lower activation energy.

• Holoenzyme: Complete enzyme with cofactor.

• Apoenzyme: Protein portion, inactive without cofactor.

• Cofactor/Coenzyme: Non-protein helper (metal ion or organic molecule).

• Competitive Inhibition: Inhibitor binds active site.

• Noncompetitive Inhibition: Inhibitor binds allosteric site.

Activation Energy and Enzyme Reaction Steps

• Activation energy is the energy required to start a reaction.

• Enzymes lower activation energy, increasing reaction rate.

ATP Cycling

• ATP stores energy in phosphate bonds; generated by substrate-level and oxidative phosphorylation.

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

Aerobic Cellular Respiration

Step	Input	Output	Cell Location
Glycolysis	Glucose	Pyruvate, ATP, NADH	Cytoplasm (both)
Krebs Cycle	Pyruvate (as Acetyl-CoA)	CO2, ATP, NADH, FADH2	Cytoplasm (prokaryotes), mitochondria (eukaryotes)
Electron Transport Chain	NADH, FADH2, O2	ATP, H2O	Plasma membrane (prokaryotes), inner mitochondrial membrane (eukaryotes)

Electron Transport Chain and Chemiosmosis

• Electrons transferred through carriers; protons pumped to create gradient; ATP synthase produces ATP.

Aerobic vs. Anaerobic Respiration

• Aerobic: Uses O2 as final electron acceptor; more ATP produced.

• Anaerobic: Uses other acceptors (nitrate, sulfate); less ATP.

Fermentation

• Partial oxidation of glucose; organic molecule as final electron acceptor; less ATP than respiration.

• Types: Lactic acid, alcoholic fermentation.

Photosynthesis

• Converts light energy to chemical energy; two steps: light reactions (ATP, NADPH), Calvin cycle (CO2 fixation).

Challenge Questions: Application to Pseudomonas fluorescens

Cell Structure

• LapA: Surface protein for attachment.

• Flagella: Multiple appendages for movement.

• Cell Wall: Gram-negative (2 lipid membranes).

• DNA: Circular in cytoplasm.

• Extracellular Layer: Sugar-protein layer, unorganized.

Cell Growth

• Oxygen requirement: Obligate aerobe.

• Optimal temperature: Mesophile (20–45°C).

• Optimal pH: Neutrophile (pH ~7).

Metabolism

• Can perform aerobic respiration; may ferment under anaerobic conditions.

Control of Microbial Growth

• Endospores: Pseudomonas fluorescens does not form endospores.

• High-level germicide required to kill; evidence from tube growth patterns.

Additional info: These notes expand on the study guide questions, providing definitions, examples, and tables for exam preparation in introductory microbiology.