Basic Bacteriology

3 basic shapes of bacteria

1. cocci (round)

2. bacilli (rods)

3. spirochetes (spiral shaped)

what determines shape of bacteria

rigid cell wall

what is one of the most important criteria used in bacteria identification

microscopic appearance of bacterium

what are the 3 arrangements of cocci

1. diplococci

2. streptococci

3. staphylococci

diplococci occur in

pairs

streptococci occur in

chains

staphylococci occur in

clusters

what is the outermost component common to all bacteria

cell wall

what is the exception of bacteria that does not have a cell wall

mycoplasma species

how is the cell wall located in comparison to the cell membrane

located externally

what is the cell wall composed of

peptidoglycan

what is the role of peptidoglycan

1. structural support

2. maintains characteristic shape of cell wall

what are some features that are external to the cell wall (some bacteria have these things)

1. LPS (endotoxin)

2. capsule

3. flagella

4. pilli

describe the difference in peptidoglycan in the cell wall of gram-positive vs gram-negative

gram-positive have thick peptidoglycan while gram-negative have thin peptidoglycan

what do gram-positive bacteria have in their cell wall that protrude outside the peptidoglycan (gram-negative bacteria do not have this)

teichoic acid

what makes up the complex outer layer of gram-negative bacteria outside of their cell wall

lipopolysaccharide (LPS, endotoxin), lipoprotein, and phospholipid

what is the name of the combined gram-negative bacteria outer layer and cell wall

envelope

what is laying between the outer-membrane layer and the cytoplasmic membrane in gram-negative bacteria

periplasmic space

what enzymes are within the periplasmic space in gram-negative bacteria

B-lactamases

role of B-lactamases

degrade penicillin and other B-lactam drugs

B-lactamases make gram-negative bacteria what in terms of sensitivity to antibiotics

less sensitive

photo showing comparison of cell walls between gram-negative and gram-positive

most important staining procedure in microbiology

gram stain

what does gram stain separate bacteria into

2 groups:

1. gram-positive stain purple

2. gram-negative stain pink/red

4 step procedure of gram stain

1. crystal violet dye stains all cells purple

2. iodine solution is added to form a crystal violet-iodine complex; all cells continue to appear purple

3. organic solvent extracts the purple dye/iodine complex from the lipid-rich, thin-walled, gram-negative bacteria to a greater degree than from the lipid-poor, thick-walled, gram positive bacteria

4. red dye (safranin) stains the decolorized gram-negative cells red/pink; the gram-positive cells remain purple

gram stain is useful in which 2 ways

1. identification

2. influencing choice of abx - gram-positive bacteria are more susceptible to penicillin (lack periplasmic space)

photo showing which bacteria you need to know (first 3 lines)

does mycobacteria cell wall stain with gram stain

no

mycobacteria are ___-fast

acid

what does mycobacteria being acid fast mean

resist decolorization with acid-alcohol after being stained with carbolfuchsin

what do acid-fast bacteria (mycobacteria) have in their cell wall

high concentration of lipids - mycolic acids

list of medically important bacteria that cannot be seen with gram stain

know mycobacteria, chlamydia, and rickettsiae

peptidoglycan is found only in ____ cell walls

bacterial

2 functions of peptidoglycan

1. important in maintaining shape of cell

2. allows cell to withstand low osmotic pressure

(complex, interwoven network that surrounds the entire cell)

why is peptidoglycan a good target for antibiotics

antibiotics inhibit the synthesis of peptidoglycan

list 3 antibiotics in particular that inhibit the synthesis of peptidoglycan

1. penicillin

2. cephalosporins

3. vancomycin

name the enzyme that is present in tears, mucus and saliva

lysozyme

role of lysozyme

contributes to natural resistance of host to microbial infection

what specific action does the lysozyme carry out

cleaves the peptidoglycan backbone of bacteria

the LPS of the outer membrane of the cell wall of gram-negative bacteria is ___

endotoxin

what is endotoxin responsible for when one has gram-negative bacterial disease

fever, shock

describe the 3 distinct units of Lipopolysaccharide

1. lipid A: phospholipid that causes toxicity

2. core polysaccharide linked to lipid A

3. O antigen: outer polysaccharide

fibers that extend from the outer layer of gram-positive cell wall

teichoic acid

what do teichoic acids induce symptom wise

inflammation, septic shock

teichoic acid activates the ____ pathway as endotoxin (LPS) in gram-negative bacteria

same

what is the role of ribosomes

site of protein synthesis

bacterial ribosomes differ from eukaryotic ribosomes in what

size and chemical composition

bacterial ribosomes are ____ in size

70S - 50S and 30S subunits

eukaryotic ribosomes are ____ in size

80S - 60S and 40S subunits

differences in the ribosomal RNAs and proteins constitute the basis of the selective action of ____ that ____ _____ ____ ____

antibiotics that inhibit bacterial protein synthesis

plasmids are

double-stranded, circular DNA molecules

plasmids replicate ____ of the bacterial chromosome

independently

do plasmids occur in gram-positive or gram-negative bacteria

both

several ____ types of plasmids can exist in one cell

different

transmissible plasmids can be transferred to cell to cell via what

conjugation

plasmids are carriers of what

medically important genes

name the medically important genes of plasmids

1. antibiotic resistance

2. exotoxins

3. pili (fimbriae)

4. resistance to heavy metals

5. resistance to UV light

6. bacteriocins

what mediates antibiotic resistance of plasmids

variety of enzymes, such as B-lactamase

what is the role of pili (coded by plasmids)

mediate adherence of bacteria to epithelial cells

what are bacteriocins

toxic proteins produced by certain bacteria that are lethal for other bacteria

transposons are

pieces of DNA that move from one site to another within or between DNAs of bacteria, plasmids, and bacteriophages

transposons are aka...

jumping genes

what do transposons code for

drug-resistant enzymes, toxins, or metabolic enzymes

are transposons capable of independent replication

no

how do transposons replicate

they replicate as part of the DNA in which they are integrated

photo showing how transposons can transfer to plasmids

what is the capsule

gelatinous layer covering the entire bacterium

what is the medical importance of the capsule

it is a determinant of virulence - limits the ability of phagocytes to engulf bacteria

capsules are used as ____ in some vaccines

antigens - can elicit protective antibodies

name 3 bacteria that have vaccines that were made using capsules

1. streptococcus pneumoniae

2. neisseria meningitidis

3. haemophilus influenzae

capsules may play a role in ____ of bacteria to human tissues

adherence

what is an important initial step in causing infection (hint: the capsule helps with this)

asherence

flagella are

long, whip-like appendages

what is the role of flagella

move bacteria toward nutrients (chemotaxis)

medical importance of flagella

some species of motile bacteria are common causes of UTIs as flagella propel the bacteria up the urethrae into the bladder

2 common bacteria species with flagella that often cause UTIs

1. Escherichia coli

2. Proteus

Pili (fimbriae) are

hairlike filaments that extend from the cell surface

pili are found mainly on gram-____ organisms

negative

medical importance of pili

1. mediate the attachment of bacteria to receptors on human cell surface (necessary step in the initiation of infection for some organisms)

2. specialized pilus (sex pilus) forms the attachment between the donor and recipient bacteria during conjugation (transmissible plasmids can be transferred from cell to cell by conjugation)

role of sex pilus

attachment between donor and recipient bacteria during conjugation

the glycocalyx is

polysaccharide coating that is secreted by many bacteria (covers surfaces like a film)

glycocalyx allows the bacteria to ___ firmly to various structures

adhere

list some structures that the glycocalyx will allow bacteria to adhere to

skin, heart valves, prosthetic joints, and catheters

glycocalyx is an important component of what

biofilms

medical importance of glycocalyx

1. glycocalyx-producing strains of Staphylococcus epidermidis and viridans streptococci cause endocartitis

2. plaque formation on teeth

bacterial spores are ____ resistant structures

highly

bacteria spores are formed by which 2 genera of gram-positive rods

1. bacillus

2. clostridium

when does spore formation occur

when nutrients are depleted

where do spores form in regards to the cell

inside the cell

what do bacterial spores contain

bacterial DNA, a small amount of cytoplasm, cell membrane, peptidoglycan, and a thick-coat

what does the thick, keratin-like coat of spores allow

resistance to heat, dehydration, radiation, and chemicals

spore has no ____ activity and can remain ___ for many years

metabolic, dormant

upon exposure to water and nutrients, what will occur in regards to the spore

specific enzymes will degrade the coat, water and nutrients will enter and germination into a pathogenic bacterial cell will occur

medical importance of spores

1. sterilization cannot be achieved by boiling

2. autoclaving is required to ensure the sterility of products for medical use

2. hand sanitizer does not kill spores; must wash hands

bacteria reproduce via what

binary fissionn

4 phases of growth cycle of bacteria

1. lag phase

2. log phase

3. stationary phase

4. death phase

what occurs in the lag phase

metabolic activity occurs but cells do not divide

what occurs in the log phase

rapid cell division occurs

what occurs in the stationary phase

nutrient depletion or toxic products cause growth to slow (number of new cells produced balances the number of cells that die)

what is the stationary phase also referred to as

steady state