Chapter 27 Part 2: Introduction to Microbiology - Focus on prokaryotes and prokaryotic cell structure

Info from Class Video

Bacteria are Prokaryotes

No nucleus or organelles bound in membranes

DNA

singular circular chromosome

no histones

Prok cell walls

of peptidoglycan

• polymer of NAG and NAM cross linked w polypeptide chain

Prok ribosome units

smaller

Proks divide by

binary fission (not mitosis)

Typical bacteria diagram (bold terms)

Glycocalyx

Bacterial chromosome/nucleoid

Pilus

Mesosome

Flagellum

Fimbriae

Inclusion/Granule

Cell wall

Cell membrane

Ribosomes

Glycocalyx

sugar coating/layer of molecules outside cell wall, not required

if tightly bound = capsule

protective (phagocytes), adhesive, receptor functions

“biofilms” slimy can’t be grabbed

prevent from drying

Bacterial Chromosome/Nucleoid

site where large DNA molecule is condensed into packet

code that directs all genetics, heredity of cell

Pilus

elongate, hollow appendage

used in transfer DNA to other cells, cell adhesion

Mesosome

extension of cell membrane folds into cytoplasm and increases surface area

Flagellum

specialized appendage attached to cell by basal body

holds long ROTATING filament

movement pushes cell forward, provides motility

Fimbriae

fine hairlike bristles from cell surface

helps adhesion to other cells and surfaces

Inclusion/Granule

store nutrients: fat, phosphate, glycogen

deposited in dense crystals or particles

can be tapped into when needed

Cell wall

semi-rigid casing provides structural support and shape for cell

macromolecule, polysacc, repeating sugars, NAG and NAM, cross linked w short AA chains

certain antibiotics work by inhibiting cell wall synthesis (penicillins)

Cell membrane

thin sheet lipid and protein

surrounds cytoplasm

controls flow materials in and out of cell pool

Ribosomes

tiny particles composed of protein and RNA

sites of protein synthesis

Plasmid

extra chromosomes - not required

can confer advantage

Eukaryotes

true nucleus and membrane bound organelles

nuclear double membrane

usually multiple chromosomes, paired, with special histone proteins associated with DNA

compartmentalization and specialized functions

if cell wall present, is chemically simple (cellulose or chitin)

slightly larger ribosome

cells divide by mitosis, meiosis

specialized sex pilus for

conjugation: transfer of copy of plasmid

Parts of a flagella

Hook (universal joint)

Filament (propeller)

Outer membrane

Bushing (L, P ring)

Stator (studs, C ring)

Inner (plasma membrane)

Rotor (S, M ring)

Monotrichous Flagella

one

Amphitrichous Flagella

multiple on one end

Lophotrichous Flagella

one on each end

Peritrichous Flagella

multiple both ends, everywhere

flagella move forward

motor rotates counter clock wise

flagella tumble, turn around

motor rotates clock wise

keep alternating until turn around

Outer membrane (outside of cell wall)

found in gram negative bacteria

Gram + vs -

+ no outer membrane

+ thick peptidoglycan cell wall

+ has acids for attachment, communication (techoic, lipotechoic)

- has outer membrane outside cell wall

- thin peptidoglycan cell wall

- have porins to allow things in

Gram -

outer membrane outside of cell wall

have LPS (lipopolysacc), lipoprotein, phospholipids, Lipid A

can cause some symptoms of - (fever, shock, diarrhea)

peiplasmic space

Peiplasmic space

fluid filled area between cell wall and outer membrane

Bacterial cell “shapes”

A - bacillus

B - round, coccus in chains ex: streptococcus

C - coccus in clusters ex: staphylococcus

D - diplococcus pairs

E - spirillum (wavy), corkscrew shape is spirochete

F - vibrio, comma shaped

cell shape determined by

org’s genetics

genes code for synthesis of cell wall material and cell division mechanism → round, rod, spiral shape

Endospores

Genus: bacillus, clostridium

hardiest of bacterial structures

hard to kill w heat/chemicals

Autoclave: heat and pressure - penetrate thick coat, destroy genome

• survives but can’t reproduce

Bergey’s Manual based on 3 primary things

1. Presence of cell wall - gram rxn + or -

2. Cell shape (morphology) - Bacillus, Coccus, Spirillum, Vibrio

3. Biochemical characteristics - sugars they ferment, enzymes ex: catalase, oxidase, decarboxylase

More modern techniques to ID specific strains

1. serological groups (antigen - antibody rxns)

2. DNA hybridization studies

3. DNA fingerprinting

4. Bacterial viruses (phage typing)