CHAPTER 4 MICROBIOLOGY

Endosymbiotic theory

The theory that some eukaryotic organelles originated from ancient prokaryotic cells living within other cells

Prokaryote

Cell without a nucleus or membrane

Eukaryote

Cell with a nucleus and membrane

Three bacterial appendages

Flagella, fimbriae, and pili

Flagella

Appendages primarily associated with motility

Fimbriae

Short structures primarily involved in attachment

Pili

Structures involved in functions including attachment and DNA transfer

Chemotaxis

Movement in response to chemicals

Phototaxis

Movement in response to light

Run

Flagellar movement associated with movement in one direction

Tumble

Flagellar movement that changes direction

Atrichous

No flagella

Monotrichous

One flagellum at one end

Lophotrichous

Tuft of flagella at one end

Amphitrichous

Flagella at both ends

Peritrichous

Flagella distributed around the cell

Periplasmic flagella

Internal flagella also called endoflagella

Capsule

Firmly attached glycocalyx

Slime layer

Loosely attached glycocalyx

Biofilm

A community of microorganisms attached to a surface and surrounded by an extracellular matrix

Quorum sensing

Microbial communication based on population density using chemical signals

Peptidoglycan

Cell wall material composed of NAG and NAM connected by peptide cross

Main cell wall functions

Maintains cell shape and prevents osmotic lysis

Gram

positive peptidoglycan

Gram

negative peptidoglycan

Gram

positive teichoic acid

Gram

negative teichoic acid

Gram

positive outer membrane

Gram

negative outer membrane

Gram

positive stain color

Gram

negative stain color

LPS

Lipopolysaccharide found in the outer membrane of Gram

Lipid A

Part of LPS associated with endotoxin activity

Bacterial DNA

Located in the nucleoid, generally as a circular chromosome

Plasmid

Small DNA molecule that replicates independently of the chromosome

Plasmid advantages

Can provide traits such as antibiotic resistance or additional metabolic abilities

Bacterial ribosome

70S

Bacterial ribosome subunits

50S and 30S

Ribosome function

Protein synthesis

Endospore

Dormant, highly resistant structure formed by certain bacteria

Endospore

forming genera

Endospore

forming bacteria

Sporulation

Formation of an endospore

Germination

Return of an endospore to a vegetative cell when conditions improve

Coccus

Spherical/round bacterial shape

Bacillus

Rod

Vibrio

Comma

Diplo

Strepto

Staphylo

Spirochete

Flexible spiral bacterium

Spirillum

Rigid spiral bacterium

Pleomorphic

Variable in shape

Virus

An acellular infectious agent that requires a host cell for replication

Virus measurement

Nanometers

Capsid

Protein coat surrounding viral nucleic acid

Capsid function

Protects viral nucleic acid and helps with interactions with host cells

Viral nucleic acid

DNA or RNA

Four viral nucleic acid combinations

Single

Viral envelope

Not present in all viruses; largely derived from host cell membrane

Naked virus

A virus without an envelope

Bacteriophage

A virus that infects bacteria

Lytic cycle

Virus replicates and causes host cell lysis/release

Lysogenic cycle

Viral genetic material becomes associated with host genetic material before productive replication

Five steps of viral multiplication

Attachment, penetration, synthesis, assembly, release