Microbiology Ch. 4 - Structure and Organization of Prokaryotic Cells

Exam 1

bacteria definition and examples

bacteria are single-celled prokaryotes (cells without nucleus) that have cell walls made of peptidoglycan and fatty acid membrane lipids

examples: chylamydia, spirochaetes, proteobacteria, gram positive bacteria

archaea definition and examples

archaea are single-celled prokaryotes (cells without a nucleus) that look like bacteria but have unique membrane lipids (branched chains with either linkages) and no peptidoglycan

often living in extreme environments

do NOT cause human diseases

examples: extreme halophiles, euryarchaeota, methanogens, crenarchaeota, hyperthermophiles

five important phyla

proteobacteria, firmicutes, actinobacteria, cyanobacteria, chlamydia

proteobacteria

(think large) largest and most diverse group of species, including e. coli and many human pathogens (gram-negative)

firmicutes

consists of many gram-positive species such as bacillus, clostridium, staphylococcus, and streptococcus

actinobacteria

(think antibiotics) include streptomyces, the genus that produces the antibiotic streptomycin (gram-negative)

cyanobacteria

(think plants) carries out photosynthesis using chlorophyll, responsible for the appearance of oxygen in earth’s early atmosphere (gram-negative)

chlamydia

(think small) extremely small, mostly pathogenic bacteria (gram-negative, but lack classic peptidoglycan wall)

archaea living characteristics

most extreme environments

may live in the absence of oxygen

cell walls lack peptidoglycan

cell membranes contain unusual lipids

euryarcheota examples

methanogens (anoxic environments), extreme halophiles (salt-lovers), and thermoacidophiles (grow in high temperatures with low pH)

crenarchaeota

grow in hot, acidic environments such as hot springs and volcanic vents

diplococci (cocci)

two spheres

example: streptococcus pneumoniae

streptococci (cocci)

long chain of spheres

example: streptococcus pyogenes

tetrad (cocci)

four spheres

staphylococci (cocci)

blanket of spheres

example: staphylococcus aureus

sarcina (cocci)

eight spheres to form a cube

example: sarcina ventriculi

chain of bacilli (bacilli)

chain of rods

example: bacillus anthracis

flagellate rods (bacilli)

single rod with protruding flagella

example: salmonella typhi

spore-former (bacilli)

rod with a spore (looks like a hole)

example: clostridium botulinum

vibros (spiral)

v-shaped rod with single flagella

example: vibrio cholerae

spirilla (spiral)

squiggly rod with multiple flagella or pili

example: helicobacter pylori

spirochaetes (spiral)

spiral-shaped rods

example: treponema pallidum

prokaryotic cell flagella

protein fibers that rotate and enable the cell to move through fluids

prokaryotic cell membrane

a lipid bilayer with proteins controlling the movement of materials into and out of the cell

prokaryotic cell wall

a semirigid structure composed of carbohydrate and protein, providing shape and structural support

tough and protective external shell

maintains cell shape and water balance

main ingredient is peptidoglycan

prokaryotic cell glycocalyx

a thick or thin layer of carbohydrates providing protection and helping with cell adhesion to surfaces

prokaryotic cell pili

thin protein fibers extending from the surface that enable adhesion to surfaces

prokaryotic cell inclusions

cytoplasmic sites for the storage of nutrients

prokaryotic cell ribosomes

a particle composed of RNA and protein involved in manufacturing proteins

prokaryotic cell cytoplasm

the semifluid substance inside the cell in which much of the cell’s metabolism occurs

prokaryotic cell nucleoid

the area containing the bacterial chromosome, which contains essential genes for growth and metabolism

prokaryotic cell plasmid

a closed loop of DNA containing nonessential genetic information

pili

fimbriae: attachment

conjugation pili: genetic transfers and antibiotic resistance genes

prokaryotic flagella

long appendages used for cell motility, chemotaxis (movement from chemical reactions), and attachment

contain flagellin filament, a hook, and a basal body

spirochetes contain…

endoflagella, which move the cell through torsion exerted by endoflagellar rotation

located between the peptidoglycan and the cell membrane

glycocalyx

thick outer layer external to the cell wall

adhering layer of polysaccharides (and sometimes proteins)

a thick glycocalyx bound to the cell is a capsule (a thick layer) and has a slime layer (diffused layer of polysaccharides)

virulence factors that help protect bacteria from phagocytosis, help with attachment, and prevent dehydration

gram-positive bacteria

(blue) have thick peptidoglycan walls with teichoic acid, no LPS, and endotoxin a

gram-negative bacteria

(red) have two-dimensional (thin) peptidoglycan layer and no teichoic acid, has LPS (lipopolysaccharide), and a part of LPS is lipid a that is also called endotoxin