Microbiology Lecture 3: Bacterial and Eukaryotic Cell Structure

Vocabulary flashcards covering bacterial cell walls, external appendages, motility modes, and basic eukaryotic cell organelles based on the lecture text.

Gram Positive

Bacterial cells characterized by a thick layer of peptidoglycan in their cell wall. Teichoic acid→hydrophilic strengthens it & promotes adhension

Gram Negative

Bacterial cells characterized by a thin layer of peptidoglycan surrounded by an outer membrane.

Teichoic Acid

A hydrophilic molecule embedded in the peptidoglycan layer of many Gram positive bacteria that strengthens the wall and aids surface adherence.

Periplasm

The fluid-filled space situated between the outer membrane and plasma membrane in Gram negative bacteria where peptidoglycan repair and molecule modifications occur.

Gram + periplasm is btw peptidoglycan layer and the inner plasma membrane

Mycobacteria (Acid-Fast Bacteria)

A group of acid fast pathogenic bacteria featuring a thick peptidoglycan layer covered by an outer layer of mycolic acid.

gram stain test does not work on mycobacteria bc of mycolic acid

Mycolic Acid

A hydrophobic, waxy layer located outside the peptidoglycan layer in acid fast bacteria that blocks stains, antibiotics, and nutrients.

Requires s[ecoa; acod-fast staining procedures, & multiple doses at higher concentrations for extended durations 4 treatment

Mycoplasmas

A group of bacteria that completely lack peptidoglycan and a cell wall, utilizing sterols in their plasma membrane to maintain structural integrity.

Sterol

Hydrophobic lipid in phospolipid bilayer. Organizes phospholipids to form a structurally sound barrier that compensates 4 no cell wall

Glycocalyx

A sticky, sugar-rich coat located outside the cell wall that aids in surface attachment, prevents desiccation, and provides defense against host immunity and viruses.

Capsule

A organized structured, firmly attached form of glycocalyx that is difficult to remove from the cell.

Slime Layer

A loose, unorganized form of glycocalyx that is easily removed from the cell surface.

Biofilm

A community of microbes embedded in glycocalyx attached to each other and anchored to a surface (teeth, rocks, catheters)

***Amplify all standard benefits of an individual glycocalyx*** -no additional features

-stronger surface tension, higher resistance to drying out, viral infection & host immunity

S-layer (surface layer)

An outer protein layer surrounding the cell structure that spontaneously assembles to protect against environmental stressors like high salt. facilitates surface attachment. Less common than glycocalx. (bc protein synthesis requires a lot of energy_

Pili

Hollow, tube-shaped protein structures anchored in the plasma membrane that extend outward beyond external cell layers (cell wall, capsule, s-layer)nto assist in attachment.

Fimbriae (Attachment Pili)

Numerous pili distributed around a bacterial cell used specifically for adhering to surfaces.

F Pilus (conjugation Pilus)

A specialized single pilus that connects a bacterial cell to another bacterium during conjugation to transfer genetic material.

Type IV Pilus

A pilus that enables twitching motility by latching onto a surface and changing its angle to drag the bacterial cell forward. (jerky twitching movement)

Taxis

Directed Bacterial movement in response to environmental stimuli (bacteria will NOT move for no reason)

Chemotaxis

Bacterial movement stimulated by chemical molecules in the environment.

Phototaxis

Bacterial movement stimulated by light.

Positive Taxis

Directional movement of a cell toward a stimulus.

Negative Taxis

Directional movement of a cell away from a stimulus.

Basal Body

The motor assembly of a flagellum composed of protein rings embedded in the cell boundary layers and a central rod. Localized in the plasma membrane, peptidoglycan, & outer membrane(in Gram -)

Hook

The curved structural component connecting the basal body rod to the flagellar filament.

Filament (Tail)

The long, rigid, spiral-shaped protein tail component of a flagellum attached to the hook extends into extracellular environment

Biased Random Walk

A navigation process where a bacterium alternates straight swims with random tumbles, biased toward or away from a stimulus based on membrane receptor signals.

Gliding Motility

Smooth, continuous movement across a surface accomplished by surface adhesins linked to internal motor proteins that roll the cell forward. No twitching or jerking

Endoflagella

Internal flagella (axial filaments) located in the periplasmic space (btw plasma membrane & pepridoglycan) of spirochetes that rotate to cause a corkscrew twirling motion.

Nucleolus

A dense, unbordered region inside the eukaryotic nucleus containing concentrated RNA used for ribosome construction.

Rough Endoplasmic Reticulum

Membranous folds continuous with the nuclear membrane that are studded with ribosomes and participate in protein synthesis.

Smooth Endoplasmic Reticulum

Membranous folds continuous with the nuclear membrane that lack ribosomes and contain membrane proteins involved in lipid synthesis.

80S Ribosomes

The size classification of eukaryotic ribosomes responsible for synthesizing cellular proteins.

Golgi Body

An organelle consisting of stacked flattened membrane discs that modifies and folds proteins in a unidirectional path and packages them into vesicles.

Vesicle

A small spherical membrane-bound sac formed by the Golgi body that fuses with the plasma membrane to secrete materials out of the cell.