Bacterial Structure

Cell Wall

Maintains bacterium shape and provides structural protection against environmental stresses.

Plasma Membrane

Controls the movement of substances in and out of the cell.

Capsule

An outer protective layer surrounding the cell wall in certain bacteria.

Nucleoid (DNA)

The region containing the primary circular genetic material.

Plasmid

Small independent circular DNA molecules that can replicate independently and carry extra genes.

Ribosomes

Cellular structures responsible for protein synthesis.

Cytoplasm

The gel-like fluid filling the cell where metabolic reactions take place.

Flagellum

A long, whip-like appendage used for movement and motility.

Pilus (Pili)

Hair-like projections used for surface attachment and genetic material transfer.

Cocci

Round, oval, or spherical-shaped bacteria that can form pairs or clusters.

Bacilli

Rod-shaped bacteria such as Escherichia coli and Salmonella.

Spirilla

Rigid, spiral, or wavy-shaped bacteria.

Pleomorphic Bacteria

Bacteria that lack a single characteristic shape and alter form based on conditions.

Gram-Staining

Differential staining technique classifying bacteria based on cell wall structural differences.

Gram-Positive Color

Retains the dye and appears purple.

Gram-Negative Color

Does not retain the dye and appears pink or red.

Peptidoglycan Layer (Gram +/-)

Thick in Gram-positive bacteria and thin in Gram-negative bacteria.

Outer Membrane (Gram +/-)

Absent in Gram-positive; present with lipids and lipopolysaccharide (LPS) in Gram-negative.

Teichoic Acids

Present in Gram-positive cell walls; absent in Gram-negative.

Antibiotic Resistance (Gram +/-)

Gram-negative is more resistant due to a protective outer membrane barrier.

Environmental Survival (Gram +/-)

Gram-positive generally survives longer in external environments.

Toxins Produced (Gram +/-)

Gram-positive produces exotoxins; Gram-negative produces endotoxins (lipid A).

Mycobacterium bovis Exception

Gram-positive bacterium with a unique lipid-rich outer membrane.

Binary Fission

Asexual reproduction where a cell replicates DNA and divides into two identical daughter cells.

Budding

Asymmetrical cell division where a small bulge forms and detaches as a new cell.

Conjugation

Direct transfer of genetic material between two bacterial cells via a pilus.

Transformation

Direct uptake and incorporation of free-floating environmental DNA into the genome.

Transduction

Transfer of bacterial DNA between cells using a bacteriophage vector.

Temperature Danger Zone

The 5°C to 60°C range where bacteria rapidly multiply.

Mesophiles

Pathogens that thrive at 20°C to 40°C, with an optimum around 37°C.

Psychrophiles and Thermophiles

Psychrophiles thrive below 20°C; thermophiles thrive above 45°C.

Temperature Extremes on Bacteria

Freezing halts growth; excess heat denatures enzymes and proteins, causing cell death.

pH Growth Range

Most bacteria prefer a slightly acidic to neutral range of pH 6.5 to 7.5.

Oxygen Requirements

Classified into aerobes, anaerobes, and facultative anaerobes based on oxygen tolerance.

Water Activity (aw)

Most species require available water with a minimum water activity greater than 0.91.

Desiccation and Osmotic Pressure

Drying causes membrane damage; high salt or sugar drives water out via osmosis.

Leptospirosis

Assigned group research pathogen caused by Leptospira spp.

Brucellosis

Assigned group research pathogen caused by Brucella spp.

Tuberculosis

Assigned group research pathogen caused by Mycobacterium spp.

Salmonella

Assigned group research pathogen caused by Salmonella enterica.

Campylobacter

Assigned group research pathogen caused by Campylobacter spp.

E. coli

Assigned group research pathogen caused by Escherichia coli.