Bacteria and Eucaryotic Pathogens Flashcards
Bacterial cell wall of gram (+) and gram (-) Bacteria:
(-)
outer plasma membrane with LPS
Periplasmic space
Peptidoglycan layer 2-8 nm (murein)
inner plasma membrane
(+)
Thick Peptidoglycan layer 20-80 nm with Teichoic acid
Inner plasma membrane
What are the factors used to characterize bacterial species?
Shape, staining pattern (gram +, gram -), Biochemistry, Physiology (growth and metabolism), genetics
Tree of bacteria: Proteobacteria
Gram-negative
Beneficial and pathogenic
Five groups: alpha, ß, gamma, delta, epsilon
Proteobacteria -> Gammaproteobacteria
most diverse group, mostly gram negative
-Pseudomonas aeruginosa
-Haemophilus influenzae
-Vibrio cholera
-Legionella pneumophila
-Enterobacteriaceae (E coli, Salmonella)
Gram Negative Pathogens (life cycle with spores)
Chlamydia trachomatis
-Eye infection, STI
-Obligate intracellular bacterium (require eukaryotic host to survive)
Gram Negative Pathogens: Spirochetes
Treponema pallidum (syphilis)
Borrelia burgdorferi (Lyme disease)
-long spiral-shaped with axial filament (flagellum) for movement
Gram-Negative Pathogens: CFB Group
Cytophaga, Fusobacterium, and Bacteroides (human gut)
anaerobic, fermenters (use substrate-level phosphorylation)
What are two large gram-positive bacteria groups, and how are differentiated?
Actinobacteria (high GC Gram +)
Firmicutes (low GC Gram -)
both include pathogens and microbiota species
Characteristics of Actinobacteria:
Mycobacterium (M. tuberculosis), Corynebacterium (C. diphtheria)
Bifidobacterium (commensal, probiotic)
aerobic, variety of cell walls
Examples of Firmicutes: Clostridia
Clostridia:
-gram + and spore-forming
-hospital pathogen, found in soil
-make toxins
-> Clostridium tetani, Clostridium botulinum
Examples of Firmicutes: Lactobacillales
includes cocci (round) and bacilli (long-shaped)
-> Streptococcus
some are beneficial Lactobacillus acidophilus (yogurt and cheese)
and some are pathogenic
Similarities between Archaea and Bacteria; Archea and Eukaryotes
Bacteria:
No organelles, unicellular, usually 1 chromosome, binary fission (asexual), small cell size, DNA stored in the cytoplasm
Eukaryotes:
Genetics structure: some Introns, some histones, complex genome
insensitive to antibiotics, multiple RNA polymerases, similar ribosomes
Bacterial characteristics beneficial for self-differentiation:
-Phosphatidylglycerol (lipid membrane): in all bacteria / humans have a lot
-Polysaccharide: in some bacteria / can also be found in human
-Lipopolysaccharide: in some bacteria / ….
-ds DNA: in all bacteria / easy to differentiate when found in cytoplasm
-Hexokinase: in most bacteria / amino acid seq. different in human different -> innate cant differentiate, adaptive can
-mRNA: n all bacteria; is not beneficial for differentiation
-Salmonella Typhi exopolysaccharide: ….
What are the 4 kingdoms of eukaryotes?
Animals, Fungi, Plants, Protists
What are examples of Protists?
-Amoeboid Protozoans
-Spore-Forming Protozoans (Apicomplexa)
-> Taxoplosmosis in cat litter, Malaria
->complex life cycle, asexual and sexual
-Flagellated Protozoans- free living (Euglena), parasitic (Trichomonas vaginalis)
What are the characteristics of Fungal Diseases?
-Disease caused by fungi is called mycoses
Mostly in Immunocompromised individuals
-but also they are also true pathogens, f.e. Histoplasmosis,
Histoplasmosis grows in soil and the spores are inhaled
-some can produce mycotoxins and cause allergies (Claviceps purpurea)
What are examples and characteristics of Parasites?
-Helminths: parasitic worms (flat or round (nematodes)
-complex life cycle, sexual reproduction
-spread in microscopic form -> Eggs ingested via fecal-oral route
What are the cellular targets of antimicrobial drugs?
-Plasma membrane -> polymyxin targets LPS -> cause destabilization and cell lysis
-prokaryotic ribosomes - Chloramphenicol 50S, Aminoglycosides 30S, Tetracyclines 30 S
-metabolic pathways - Sulfonamides inhibits folic acid production, Isoniazid prevents synthesis of mycolic acid
-DNA/RNA synthesis -> Rifamycin bacterial RNA polymerase
-cell wall (peptidase blocked)
Which type of drugs may cause side effects and why?
Drugs targeting Fungi and Protists, bc they are more similar to human than bacteria are
What different steps of infection can antivirals block?
Attachment
Penetration
Uncoating
Replication and assembly
Release
What agents are used by antivirals?
-Nucleotide analogs -> also target human system (limited time use)
-other immune components: Human rabies immunoglobin
(HRIG), interferon-alpha (cytokine shutting down protein synthesis of infected cells)
What substance is found in fungi but not in humans and what antifungal agents?
A sterol called ergosterol in the fungal cell membrane
Anti-fungal drugs:
* Azoles (imidazoles and triazoles)
* Allyamines
* Polyenes
What are drugs inhibiting cell wall synthesis of fungi?
Echinocandin drugs: target the enzyme making beta-glucan
Polyoxins and nikkomycins: target chitin synthesis
Why is it difficult to develop antiprotozoal and
antihelminthic drugs?
-These parasites are eukaryotes, components are closer to human, and bc of complex life cycles
-All antimicrobials have increasing resistance issues
