Microbiology Lecture Flashcards: Bacterial Motility, Genetics, and External Structures

Vocabulary flashcards covering bacterial chemotaxis, motility, genetics notation, conjugation, horizontal gene transfer, pili, capsules, and biofilms.

Sensor-regulator pairs

Protein systems located in the cytoplasmic membrane that detect environmental signals, such as sugars or toxins, and transmit them into the cell via chemical modifications like phosphorylation.

Motility agar

A soft, soupy agar medium formulated with a reduced solidifying agent to allow motile bacteria to swim through it and form expanding colonies.

Wild type

The natural, non-mutated strain or form of an organism as it is typically isolated from nature.

Bacterial genetic notation

The standard convention where lowercase, italicized letters designate a gene (e.g., cheB), while a capitalized, non-italicized string designates the protein product (e.g., CheB).

Plasmid

A small, circular, double-stranded extrachromosomal DNA element that carries genes separate from the bacterial chromosome.

Complementation

The restoration of a mutant bacterial phenotype by introducing a functional copy of the deleted or mutated gene on a plasmid.

Promoter

A specific DNA site that initiates transcription of a gene, controlling the rate at which its encoded protein product is produced.

Flagellar run

The forward swimming motion of a bacterium produced when its flagella rotate in a counterclockwise direction.

Flagellar tumble

The random reorientation of a bacterium that occurs when its flagella rotate in a clockwise direction.

Endoflagella

Internal flagellar structures, also known as axial filaments, found in spirochetes that twist inside the cell to rotate the body like a corkscrew for movement.

Leptospira

A genus of spirochete bacteria excreted in infected animal urine that can cause leptospirosis in humans through contact.

Attachment pili

Small, hollow protein structures on the bacterial surface (also called fimbriae) that enable cells to adhere to host tissues and inanimate surfaces.

Conjugation

A form of direct bacterial mating where DNA, typically a single strand of a plasmid, is transferred from a donor cell to a recipient cell.

Conjugation pilus

A hollow protein tube (also known as an F pilus) constructed by a donor bacterium to attach to a recipient cell during DNA transfer.

Horizontal gene transfer

The transfer of genetic material between contemporaneous adult bacterial cells, as opposed to inheritance from parent to offspring.

Vertical gene transfer

The passage of genetic material directly from a parent organism to its offspring through cell division or replication.

F+ cell

A donor bacterial cell containing the fertility plasmid ($F$ plasmid) that possesses the genes required to form a conjugation pilus and transfer DNA.

F- cell

A recipient bacterial cell lacking the fertility plasmid ($F$ plasmid) that can receive DNA during bacterial conjugation.

Pellicle

A surface film or floating clump of bacterial cells formed at the air-liquid interface of a liquid culture.

Glycocalyx

An outer layer of extracellular polysaccharides secreted by bacteria, encompassing both dense capsules and loose slime layers.

Capsule

A dense, organized gel-like layer of extracellular polysaccharides surrounding a bacterium that protects it from dehydration, immune defenses, and antibiotics.

Slime layer

A loose, unorganized layer of extracellular polysaccharides secreted by bacteria that provides lubrication and aids in surface adherence.

Biofilm

A complex, structured community of microorganisms embedded within a self-produced matrix of extracellular polymeric substances attached to a surface.