Lecture 1: Bacterial Structure and Function Flashcards
What is Bacteria?
- Single celled organisms
- Contain both RNA and DNA
- They reproduce by binary fussion
- Cytoplasm with no nucleus
- Ribosomes -> metabolic activity
- Colonize your skin, mouth, hair, gut, and genital tract (pretty much everywhere)
3 Ways Bacteria can be Described
- Shape
- Gram Stain
- Morphology
Types of Bacteria Shape
- Cocci (circles)
- Bacilli (oval)
- Curved (squiggles)
- Spiral (wavy)
Types of Gram Stain
- Gram +’ve: Thick, purple
- Gram -‘ve: Thin, pink
How is Bacteria named by genus and species?
“Kings Play Chess On Fancy Green Squares”
Kingdom, Phylum, Class, Order, Family Genus, Species
- Genus name capitalized, species name not capitalized
*Both italicized
Gram Negative Stain
- Have a outer membrane
- Thin peptidoglycan layer
- Stain pinkish
Gram Positive Stain
- Thick peptidoglycan layer; that is cross-linked between N-acetyl Glutamine and N-acetyl Muramic acid
- Stain purplish
Characteristics of the Cell Membrane
- Energy production
- Nutrient processing
- Transport of nutrients and waste
- Selective transport of molecules
- Site of secretion of toxins and enzymes
- Osmotic barrier
What bacterium cannot be classified as either gram positive or gram negative?
Mycobacterium (known as acid fast bacteria)
ex. Mycobacterium tuberculosis
- Have thick membrane capsule and mycolic acid cell wall that make them impermeable to most things
Notable Acid-fast Bacilli (Mycobacteria)
- Mycobacterium tuberculosis (TB), Mycobacterium leprae (leprosy)
Characteristics of Mycoplasma spp.
- Genus: Mycoplasma
- Simplest of bacteria: do not have a peptidoglycan layer
- Only a lipoprotein membrane (can’t be stained)
- Do not stain at all (gram stain or any other stain)
3 Medically Relevant Gram Positives cocci (GPC)
- Streptococci
- Staphylococci
- Single cocci
Staphylococcus Characteristics
- “Grape-cluster berry”
- Gram positive bacteria are found on skin but also highly pathogenic organisms
- 2 major groups:
- Coagulase positive Staphylococcus: S. aureus
- Coagulase negative Staphylococcus: all NON S.aureus (less than +’ve)
What is the medical relevance of Gram Positives cocci Staphylococcus aureus?
- Can cause infections: several medically serious infections
- But also part of the normal flora of various areas of the body
- Always important when found in sterile site
- Methicillin Resistant S. aureus (MRSA) is a super bug
Common coagulase negative staphylococcus
- S. epidermidis, S. hominus, S. warneri, S. hemolyticus, S. capitis
What is the medical relevance of Gram Positives cocci Staphylococcus species?
- Gram positive usually found in the mouth and the oropharynx
- Typically organisms of low virulence
- Classified based on how the organisms grow on blood agar (5% blood in the agar)
Alpha hemolysis
Partial lyses of blood cells in the agar (agar goes green)
Example: Viridans Streptococci, Streptococcus pneumoniae
Beta-hemolysis
Complete lysis of blood cells in the blood agar
Example: Streptococcus pyogenes (Group A), Streptococcus agalactaea (Group B), others - Group C, Group F, Group G
Gamma-hemolysis
Blood cells not lysed (not rly hemolysis)
Example: Enterococci spp. (Group D)
Common Gram Positive Bacilli
- Bacillus anthracis, Bacillus cereus, Listeria monocytogenes, Clostridium difficile, Clostridium perfringens, Clostridium tetani, Clostridium botulinum, Propionibacterium acnes
What is Listeria monocytogenes?
(Food borne outbreaks from reheating food)
- Found in almost all soft cheeses, and deli meats
- Can cause many problems with birth and pregnancy
- Grows well at 40 celsius - cold amplification
What is Clostridium spp.
- All anaerobes (oxygen free)
- Organisms form spores, allowing them to remain in the environment for long periods of time
- Causes many infections
- Prodigious toxin producers - their primary virulence factor
Notable Clostridium spp.
Clostridium difficile, Clostridium tetani, Clostridium botulinum, and Clostridium perfringens
Characteristics of Gram Negative Bacilli
- Found in a # of sites including fresh water, the gastrointestinal tract
- Can lead to a very serious infections at a number of sites including in blood, wound infections, and pneumonia
- Major issue with these is their resistance to antibodies
Notable Gram Negative Bacilli
- Escherichia coli
- Pseudomonas aeruginosa
- Klebsiella pneumoniae
- Proteus mirabilis
Characteristics of Gram Negative Cocci
- Organisms found in the oral flora and mucosal surfaces including the genital tract
- Colonize the oral flora, but can also cause meningitis, pneumonia, bacteremia, and sexually transmitted infection
Notable Gram Negative Cocci
- Neisseria gonorrhoea
- Neisseria meningitidis
- Neisseria spp.
