LAB 5- BIOL 251

Glycocalyx

A mixture of polysaccharides and polypeptides, can be in both gran positive and negative

Slime layer

Loosely bound glycocalyx

Capsule

Well organized and tightly bound glycocalyx

Virulence factor

Increases likelihood of an infection and disease, ex: capsule

Phagocytosis

Process used by cells to engulf and digest large particles such as bacteria

Opsonization

Coating bacteria with complement proteins and antibodies to facilitate phagocytosis

Biofilms

Community of microbes that stick together in a surface with increased virulence and antibiotic resistance

Capsule layer

Clear white halo around cells

Endospores

Structures that form inside of some bacteria, a dormant form of a bacterial cell to survive harsh environments

Germination cycle

Process of producing reproductive bacteria in favorable conditions

Examples of genera that form endospores

Bacillus and clostridium

Sporulation cycle

Process of endospore formation, beginning when there is signal to turn on spore forming gene

What agents destroy endospores?

Autoclaves, sterilizing gases and liquids, ionizing radiation

Endospores can be stained:

Blue or clear

Flagella

Appendages that allow bacteria to move in their environments

What are flagella composed of?

Protein called flagellin

Flagella arrangements

Monotrichous, lophotrichous, amphitrichous, peritrichous

Monotrichous

Single flagellum at one pole

Lophotrichous

Several flagella at one pole

Amphitrichous

One flagellum at each pole

Peritrichous

Many flagella all around cell

How do flagella cause motility (see text)? Why can’t we observe flagella as they are moving?

Flagella cause motility by rotating like tiny propellers, pushing or pulling the bacterial cell through liquid. We can’t observe them moving under a light microscope because flagella are extremely thin (below the resolution limit) and move too rapidly to be seen directly.

What is chemotaxis?​Do all bacteria exhibit chemotaxis?

It is the movement of bacteria toward favorable stimuli (like nutrients) or away from harmful ones (like toxins) using their flagella. Not all bacteria exhibit this—only motile species with the necessary sensory and flagellar systems can do so.