Overview of microbio

prokaryotic

rigid cell wall-determines cell shape

no nucleus or membrane-bound organelles

ex: chlamydia

taxonomy of bacteria

all organsims have a name consisting of two parts: genus and species

ex: Streptococcus pneumoniae

gram stain results

gram + organisms: absorb crystal violet and hold onto it—→ blue

gram - organisms: violet crystal gets washed off by the alc and cells absorb safranin——> red

difference between gram + and gram -

cell wall structure

gram positive cell wall

thick homogenous sheath of peptidoglycan, contains tightly bound acidic polysaccharides (techoid and lipotechoic acid)

gram negative cell wall

contains outer membrane layer with porins (protein molecules found in upper portion of outer membrane), thinner shell of peptidoglycan that contains specialized lipopolysaccharides and lipoproteins

cell membrane in gram + and gram - is similar

flexible lipid bilayer sheet with embedded proteins

provides site for nrg rxns, nutrient processing and metabolic activities (respiration, ATP synthesis

transport regulation- main function

implications of difference in cell envelope (cell wall) structure

outer membrane in gram - bacteria provides an extra barrier makes it more impermeableto some antimicrobial dyes/disinfectants which makes it more difficult to kill

atypical bacterial structure

certain bacteria lack the cell wall structure of either gram + or gram - cell wall altogether

they still stain + or - in the gram stain

ex: mycoplasma, chlamydia

mycobacteria

-cell wall composed of unique type of lipid- mycolic acid

-cell wall is thick and waxy-high degree of resistance to certain chemicals and dyes

-acid-fast stain: used to identify these organisms

—> hot carbol fucsin stain becomes attached to cell so acid-alc solution doesn’t remove dye- this is due to high lipid conc in cell wall

spirochetes

-gram - cell wall

• too small to be seen with light microscope needs darkfield microscope

• slender and tightly coiled

• along with thin peptidoglycan cell wall, also have extra lipopolysaccharide membrane- protects them from immune recognition

  • ex: treponema pallidum

bacterial morphology- cocci

spherical (oval or bean shaped)

may be arranged in cluster chains or cubical packets

bacilli

cylindrical shape (rod)

arranged as single cells or in pairs

spiral-shaped

common-shaped, S-shaped, rigid helix, flexible helix

some have flagella that propel them forward

pleomorphic shape

lacking a distinct shape

7 groups of gram positive stain

four of the 7: bacillus, clostridium, corynebacterium, listeria

three of the 7: streptococcus, enterococcus, staphylococcus

groups of gram - stain

one group of cocci: neisseria

one group of spiral-shaped: spirochetes

rest of gram - are: rods/pleomorphic

bacterial oxygen

bacteria need 3 nzms to break down harmful oxygen products formed during oxygen’s reactions: catalase, hydrogen peroxidase, superoxidase dismutase

• those that do not contain the three nzms for oxygen breakdown

  • those that do have the three nzms necessary to breakdown oxygen need oxygen to live while those that do not cannot grow in oxygen presence

obligate aerobes

use oxygen in their metabolic processes and have all three nzms

ex: mycobacterium tuberculosis

obligate anaerobes

lack the metabolic nzm system

ex: clostridium species

facultative anaerobes

do not require oxygen for metabolism- in absence of oxygen it adopts anaerobic mode of metabolism- fermentation

ex: gram negative intestinal bacteria and staphylococci (E. coli)

microaerophilic bacteria

use very small amounts of oxygen, live in mud/waters/human body

enviornments provide a little oxygen but not directly exposed to atmosphere

ex: helicobacter pylori

virulence of organisms

depends on presence of certain factors that aid bacteria in pathogenic processes:

• cell sturctures: pili, flagella, capsules, endospores, biofilms, biofilms

• endotoxins

• exotoxins

flagella

allow for movement of microorganisms, propelling them forward

pili

straight filaments arising from bacterial cell wall

help bacteria in the adhesion process

capsules

protective walls that surround the bacterial cell membranes

makes it impossible for neutrophils and macrophages to phagocytize the bacteria the bacteria

capsules

protective walls that surround the bacterial cell membranes

make it impossible for neutrophils and macrophages to phagocyt