Gram Positive Bacteria

What are the two main groups of Gram-positive bacteria, and how are they distinguished?

actinobacteria: High GC content (>50%).

Firmicutes: Low GC content (<50%)

Firmly Close Backdoors; Listen, Staff & Strep Might enter

Firmly → Firmicutes

Close → Clostridium (Pathogenic, anaerobic, central spore-former, causes botulism, tetanus, C. diff)

Backdoors → Bacillus (Pathogenic/non-pathogenic, aerobic, off center, fastidious spore-former, B. anthracis - anthrax)

Listen → Listeria (Pathogenic, foodborne, can grow at refrigeration temps, causes meningitis)

Staff → Staphylococcus (Pathogenic, MRSA, skin infections)

Strep → Streptococcus (Pathogenic, strep throat, pneumonia, rheumatic fever)

Might → Mycoplasma (Pathogenic, atypical pneumonia, smallest bacteria, lacks cell wall)

What are some key genera of Actinobacteria, and what are their characteristics?

Mycobacterium: Contains mycolic acid (similar to fungi).

Corynebacterium: Causes diphtheria.

Propionibacterium: Used in cheese production and causes acne.

Streptomyces: Produces antibiotics

ACTIN’ Makes Cool People Shine

ACTIN’ → Actinobacteria

Makes → Mycobacterium (Pathogenic: M. tuberculosis, M. leprae – acid-fast due to mycolic acid)

Cool → Corynebacterium (Pathogenic: C. diphtheriae – diphtheria toxin)

People → Propionibacterium (Now Cutibacterium acnes, causes acne – skin flora)

Shine → Streptomyces (Non-pathogenic, soil bacteria, produces antibiotics like streptomycin)

Mycobacterium sp.

obligate aerobes and non motile. rod shape and have mycolic acid. ROE is respiration.

Mycobacterium tuberculosis

Causes tuberculosis (TB).

targets macrophages and dendritic cells

Forms granulomas in the lungs (clusters of macrophages).

Slow-growing: Doubling time of 15-20 hours

Mycobacterium Leprae

Red blotchy lesions

local anesthesia

Delayed hypersensitivity to lepromin

Corynebacterium diphtheriae

Causes diphtheria.
Polymorphic and palisades arrangement

Two stages:

Local infection: Pseudomembrane in the respiratory tract or as deep and erosive ulcer.

Systemic infection: Diphtherotoxin causes toxemia

Coryne Causes Cough

Corynebacterium causes diphtheria with a cough

Propionibacterium sp.

Have an enzyme that synthesizes propionic acid. They are anaerobes

Propionibacterium acnes

Aerotolerant anaerobe that lives in skin pores.

Uses sebum as an energy source.

Causes acne when sebum production is excessive

Streptomyces

Largest genus of Actinobacteria. Forms spores and found in soil and decaying vegetation.

Produces natural antibiotics (e.g., streptomycin, tetracycline).

Forms aerial hyphae (similar to mold)

Firmicutes bacteria phylum

Pathogenic genera: Clostridium, Bacillus, Listeria, straphlococcus, streptococcus and mycoplasma

Non-pathogenic genera: Lactobacillus.

Bacillus sp

aerobic, catalase postive, central endospore, non-fastidious

Clostridium sp

anaerobic, catalase negative, spores off center and fastidious

Bacillus anthracis

Firmicutes
Causes anthrax. ROE cutaneous, respiratory

Produces lethal factor (causes cell lysis) and edema factor (causes tissue swelling)

Bacillus subtilis

non-pathogenic

model organism

fast growing with many industrial applications

Bacilus megaterium

non-pathogenic

massive and used for endospore staining

Clostridium perfringens

pathogenic

anerobic

causes myonecocrosis

non-penetrative therefore uses lechitinase. a toxin that causes cell death

treatment using a hyperbaric chamber

Clostridium botulinum

Causes botulism (flaccid paralysis).

Produces botulinum toxin, which prevents muscle contraction

releases gas

Clostridium tetani

Causes tetanus (lockjaw).

Produces tetanospasmin, which prevents inhibitory neurons from functioning

Clostridium difficile

Firmicutes

Antibiotic resistant and grows uncontrollably when by itself

Listeria monocytogenes

Causes listeriosis.

Route of infection: Fecal-oral.

Can cross the placental barrier, affecting fetuses

Lactobacillus sp.

non pathogenic

in yogurt

Staphylococcus aureus

Causes skin infections, osteomyelitis, and MRSA (methicillin-resistant S. aureus).

Forms biofilms

Streptococcus pyogenes

strep throat, scarlet fever, Acute bacterial endocarditis and necrotizing fasciitis

Enterococcus sp.

Infected caused by dysbiosis (overpopulation)

Mycoplasma

Lacks a cell wall.

Pleomorphic and very small (0.3-0.8 µm).

Causes atypical pneumonia

Mycoplasma: No Wall, Small Ball

Lacks a cell wall and is very small