Bacteria

Nucleoid

Contains the bacterial DNA, which is typically a single, circular chromosome.

Plasmid

Small, circular DNA molecules that carry extra genes separate from the bacterial chromosome.

Ribosome

Synthesizes proteins by translating mRNA into amino acid sequences.

Cell Membrane

Encloses the cytoplasm and regulates the transport of substances in and out of the cell.

Cell Wall

Provides structural support and protection to the cell.

Capsule

A sticky outer layer that enhances the bacterium's ability to cause disease.

Flagella

Long, whip-like appendages that enable the bacteria to move.

Pilus

Short, hair-like structures on the cell surface involved in attachment and genetic material transfer via conjugation.

Endotoxins

Toxic substances released when the bacterial cell is disrupted or destroyed.

Gram-positive

Bacteria with a thick peptidoglycan layer in their cell wall, which stains purple in a Gram stain.

Gram-negative

Bacteria with a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides (LPS), which stains pink in a Gram stain.

Inhibition of Protein Synthesis

Some antibiotics bind to the ribosome, blocking the attachment of tRNA and preventing protein synthesis.

Inhibition of Folic Acid Synthesis

Some antibiotics prevent the synthesis of folic acid by competitively inhibiting the incorporation of PABA into folic acid.

Inhibition of Cell Wall Synthesis

Some antibiotics inhibit enzymes involved in the final steps of cell wall synthesis, preventing peptidoglycan strands from connecting.

Inhibition of DNA Replication

Some antibiotics inhibit topoisomerases, which maintain the supercoiling of chromosomal DNA, thus preventing essential cell processes.

Antibiotics and Viruses

Antibiotics cannot be used to treat viruses because viruses have different structures and mechanisms than bacteria; antibiotics target bacterial-specific processes.

Antibiotic Resistance

The ability of a bacterium to withstand the effects of an antibiotic.

Growth on Petri Dish (Resistance)

A resistant bacterium will grow on a petri dish exposed to the antibiotic.

Antibiotic Susceptibility

The vulnerability of a bacterium to an antibiotic.

Growth on Petri Dish (Susceptibility)

A susceptible bacterium will not grow on a petri dish exposed to the antibiotic.

Zone of Inhibition

A clear area around an antibiotic disk on a petri dish, indicating that the antibiotic is effective against the bacteria.

Determining Effectiveness (Antibiotic A)

Most effective treatment since having the largest zone of inhibition.

Determining Effectiveness (Antibiotic B)

Bacterial strain is resistant to this antibiotic since there is no zone of inhibition around this antibiotic.

Conjugation

Direct transfer of genetic material (usually a plasmid) between two bacterial cells via a pilus.

Transformation

Uptake of free DNA from the environment by a bacterial cell.

Transduction

Transfer of genetic material from one bacterium to another by a bacteriophage (virus that infects bacteria).

Target Modification

Bacteria alter the structure of the antibiotic's target site, reducing its affinity for the antibiotic.

Enzymatic Inactivation

Bacteria produce enzymes that degrade or modify the antibiotic, rendering it inactive.

Reduced Permeability

Bacteria decrease the permeability of their cell membrane, preventing the antibiotic from entering the cell.

Efflux Pumps

Bacteria use efflux pumps to actively pump the antibiotic out of the cell, reducing its intracellular concentration.

Bypass Pathways

Bacteria develop alternative metabolic pathways that bypass the steps inhibited by the antibiotic.

Predicting Bacterial Growth Patterns

The experiment involves two strains of E. coli: E. coli I contains a plasmid gene coding for ciprofloxacin resistance, and E. coli II contains a chromosomal gene coding for penicillin resistance.