Bacteria Classification & Structure

Prokaryotes vs. Eukaryotes

• Prokaryotes have a simple design and are generally smaller than eukaryotes.
• Eukaryotic cells include fungi, animals, and plants, characterized by membrane-bound organelles and a true nucleus.

Eukaryotic Traits

• Larger than prokaryotes with complex structures, including multiple diploid chromosomes.
• Membrane-bound organelles present, including mitochondria for respiration.
• Cell walls in fungi contain chitin; capable of sexual and asexual reproduction.

Prokaryotic Traits

• Bacteria that are smaller and simpler than eukaryotic cells.
• Lack a membrane-bound nucleus; possess a single haploid circular chromosome.
• Contain peptidoglycan in their cell walls, crucial for maintaining structure.

Clinical Significance of Peptidoglycan

• Unique to bacterial cell walls, making it an effective target for antibiotics.

Classification of Bacteria

• Based on macroscopic/microscopic appearance, growth/metabolic properties, antigenicity, and genetic properties.

Macroscopic Appearance

• Analyzed through growth characteristics on selective media, which includes colony morphology like size, shape, and sugar fermentation.

Basic Bacterial Shapes

• Cocci: round spheres.
• Bacilli: rod-shaped.
• Spirillum: spiral-shaped.

Bacterial Arrangements

• Cocci and Bacilli arrangements: pairs, chains, or clusters.
• Example of Spirochete includes Borrelia and Treponema.

Gram Staining Technique

• Differentiates bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall structure.

Organisms Not Classified by Gram Stain

• Mycobacterium (due to waxy coat).
• Mycoplasma (lacks peptidoglycan).
• Chlamydia (spore-like).
• Treponema (very thin).

Steps of Gram Staining

• Use Crystal Violet (Gram+ turns purple, Gram- absorbs temporarily).
• Iodine is applied to enhance staining.
• Decolorizer (Alcohol/Acetone) removes purple from Gram- bacteria.
• Apply Safranin Red, which stains Gram- pink/red while Gram+ remains purple.

Visual Characteristics

• E.coli: short rods that lightly stain.
• S.aureus: darkly staining clusters of cocci.

Clinical Significance of Gram Staining

• Essential for determining appropriate antibiotic treatment based on bacterial characteristics (e.g., Staphylococcus vs. Streptococcus).

Growth/Metabolic Properties

• Examined through oxygen requirements (aerobic vs. anaerobic), substrate utilization (fermenters vs. non-fermenters), and enzyme production.

Antigenicity

• Defined by the presence of unique surface antigens on bacterial cells.

Serotyping

• Method to distinguish bacterial strains using antibodies that detect specific antigens.

Genetic Properties

• Identified through conserved and variable DNA sequences that aid in classifying bacteria into genus and species.

Prokaryotic Mutations

• Any mutation in a prokaryotic mother cell is always expressed in daughter cells, as they are clones.

Prokaryotic Genetic Material

• Chromosome found in the cytoplasm; no membrane-bound organelles and transcription coupled with translation.

Cytoplasmic Membrane Functions

• Similar to eukaryotes but lacks sterols; involved in electron transport, ATP production, uptake, secretion, and cell division.

Cell Wall Characteristics

• Outermost component in all bacteria except Mycoplasma, critical for structural integrity and preventing osmotic lysis.

PAMPs

• Pathogen-Associated Molecular Patterns trigger innate immune responses due to repetitive structures on bacteria.

This quiz covers the classification and structural differences between prokaryotes and eukaryotes. It includes true/false questions and details about eukaryotic traits, providing a comprehensive overview of microbial biology. Perfect for biology students looking to enhance their understanding of microorganisms.