Microbiology Fundamentals and Biochemistry Basics: Structured Study Notes

Microorganisms: Definition and Classification

Definition and Examples

Microorganisms are microscopic organisms that are often invisible to the naked eye. They include a diverse group of life forms studied in microbiology.

• Bacteria: Prokaryotic; unicellular; can be pathogenic or nonpathogenic.

• Archaea: Prokaryotic; unicellular; nonpathogenic; often found in extreme environments.

• Protists: Eukaryotic; unicellular and multicellular; can be pathogenic or nonpathogenic (e.g., amoebae, algae).

• Fungi: Eukaryotic; unicellular (yeast) and multicellular (mushrooms); pathogenic and nonpathogenic.

• Helminths: Eukaryotic; multicellular; parasitic roundworms and flatworms.

• Prions: Infectious proteins; not cells; can infect animal, plant, or bacterial cells; have DNA or RNA genomes; not discovered until the 1980s; transmitted by transplant or ingestion; some prion diseases are inherited.

Additional info: Viruses are also studied in microbiology, though not listed above. They are acellular infectious agents.

Pathogens and Disease

True Pathogen vs. Opportunistic Pathogen

True pathogens are microbes that cause disease in healthy individuals. Opportunistic pathogens cause disease only in weakened hosts.

Spontaneous Generation vs. Biogenesis

• Spontaneous Generation: The outdated idea that life arises from nonliving matter.

• Biogenesis: The theory that life arises only from pre-existing life.

• Key Experiment: Louis Pasteur's swan-neck flask experiment disproved spontaneous generation by showing that microbes did not grow in broth unless exposed to air containing microorganisms.

Koch's Postulates

Koch's postulates are a series of criteria used to establish a causative relationship between a microbe and a disease:

1. The organism must be present in every case of the disease.

2. The organism must be isolated from the diseased host and grown in pure culture.

3. The cultured organism should cause the same disease when inoculated into a susceptible host.

4. The organism must be re-isolated from the inoculated, diseased animal.

Major Contributors to Microbiology

The following table summarizes key figures and their contributions:

People/Scientist	Contributions
Florence Nightingale	Established aseptic techniques in nursing; founded modern nursing
Anton van Leeuwenhoek	Observed bacteria
Edward Jenner	Vaccinated against smallpox
Alexander Fleming	Discovered penicillin
Louis Pasteur	Disproved spontaneous generation and showed biogenesis is responsible for propagation of life

Scientific Method in Microbiology

Definition and Steps

The scientific method is a systematic way of exploring questions through investigation.

1. Hypothesis

2. Collect data

3. Make observations

4. Analyze the data

5. Make a conclusion

Hypothesis vs. Prediction: A hypothesis is a tentative explanation; a prediction is a specific, measurable outcome expected if the hypothesis is true.

Scientific Law vs. Theory

• Law: Describes what happens.

• Theory: Explains how and why something happens.

Taxonomy and Nomenclature

Binomial Nomenclature

Scientific names use a two-name system: Genus and Species.

Taxonomic Hierarchy

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Microbial Interactions

Parasitism, Mutualism, and Commensalism

• Mutualism: Both partners benefit.

• Commensalism: One benefits, the other is unaffected.

• Parasitism: One benefits at the expense of the other.

Role of Normal Microbiota

Normal microbiota consists of bacteria found in and on the body. Disruption can lead to disease, as beneficial bacteria may be killed, allowing harmful bacteria to thrive and cause illness.

Antibiotic Resistance and Population Genetics

Some bacteria are resistant to antibiotics due to genetic mutations. For example, sickle cell trait provides resistance to malaria.

Laboratory Techniques in Microbiology

Aseptic Technique

Aseptic technique involves practices to prevent contamination during microbial work, such as using sterile tools and protective equipment.

Staining Techniques

• Simple Staining: Uses a single dye to make cells and their components more visible.

• Differential Staining: Uses multiple dyes to distinguish between different types of bacteria.

Gram Staining

Gram staining is a differential technique that categorizes bacteria into two groups:

• Gram-positive: Purple stain; thick peptidoglycan layer.

• Gram-negative: Pink stain; thin peptidoglycan layer and outer membrane.

This helps diagnose bacterial infections and determine appropriate antibiotics.

True/False Statements on Microbiology

• Normal microbiota colonies are not always even on both sides of the body. (F)

• Gram-positive bacteria have a thick peptidoglycan layer. (T)

• Samples can be stained or unstained for light microscopy. (T)

• Gram-negative bacteria have a thin peptidoglycan layer. (T)

• Immersion oil improves resolution by limiting light refraction. (T)

Chapter 2: Biochemistry Basics

Atoms and Subatomic Particles

An atom is the smallest unit of an element that retains its chemical properties. Atoms are made up of:

• Proton: Positively charged particle

• Neutron: Neutral particle

• Electron: Negatively charged particle

Atomic Mass and Atomic Number

• Atomic Number: Number of protons in the nucleus

• Atomic Mass: Sum of protons and neutrons

Cations and Anions

• Cation: Positively charged ion (loses electrons)

• Anion: Negatively charged ion (gains electrons)

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons. Medical isotopes are used for diagnosis and treatment.

Molecules and Compounds

• Molecule: Formed when two or more atoms are chemically bonded.

• Compound: A molecule composed of two or more different elements.

Organic Molecules

A molecule is considered organic if it contains carbon-hydrogen (C-H) bonds. Common organic functional groups include:

• Hydroxyl

• Carbonyl

Acids, Bases, and pH

• Acids: pH below 7; turn litmus paper red.

• Bases: pH above 7; turn litmus paper blue.

• pH Scale: Ranges from 0 to 14; logarithmic scale; 7 is neutral.

Buffers

Buffers stabilize pH by absorbing or releasing H+ ions.

Chemical Bonds

• Covalent Bond: Sharing of electrons between atoms.

• Ionic Bond: Transfer of electrons from one atom to another, resulting in oppositely charged ions.

• Hydrogen Bond: Weak bond between a hydrogen atom and an electronegative atom (e.g., oxygen, nitrogen).

Electron Shells and Reactivity

The following table shows the number of electrons and outer shell electrons for selected elements:

Element	Number of Electrons	Number of Electrons in Outer Shell for Reaction
Lithium (Li)	3	1
Chlorine (Cl)	17	7
Carbon (C)	6	4
Phosphorus (P)	15	5
Magnesium (Mg)	12	2

Hydrophobic, Hydrophilic, and Amphipathic

• Hydrophobic: Water-fearing

• Hydrophilic: Water-loving

• Amphipathic: Both hydrophobic and hydrophilic regions

Catalysts in Biological Systems

Catalysts are substances that speed up chemical reactions without being consumed or altered in the process.

Additional info: Enzymes are biological catalysts essential for metabolic processes.