29 terms

Micro - (lec 6)Bio of Atypical Bacteria & Fungi Intro

lec 6
Atypical bacteria
Mycoplasma, Rickettsiae, Anaplasma & Coxiella & Chlamydiada
Mycoplasma: size
Smallest known free-living organism
0.15 -0.3 micrometer
Does mycoplasma possess a call wall?
No. Does not synthesize peptidoglycan (but will stain pink on gram staining.
What is the unique feature re: mycoplasma cytoplasmic membrane
contains sterols (integrity & strength)
Mycoplasma Attachment Organelle
P1 Adhesin (allows attachment to epithelial cells lining resp & urogenital tract --> tissue destruction dt H2O2 & superoxide anion.
What would happen if mycoplasma lost it's P1 Adhesin?
loss of virulence.
bacilli - coccoidal (pleomorphic)
closely related to gram -ve (do not stain well)
Unique feature of Rickettsiae
Obligate intracellular
unable to prod. sufficient energy to replicate
CANNOT be cultured on AGAR
This is because it does not possess Coenzyme A, NAD or ATP - all obtained from host.
Is Rickettsiae Zoonotic?
yes, spread via arthropod vectors (ticks, lice, fleas, mites)
Anaplasmataceae & Coxiella
Obligate intracellular pathogens
2 groups: 1) human infections only 2) Zoonotic infections (birds -- > man) (weird)
Unique feature of Chlamydia
Obligate intracellular pathogens
Grow in cytoplasmic vacuoles in limited host cell types
Depend upon host for ATP & NAD
Cannot synthesize ATP or reoxidize NADP
No detectible flavoproteins or cytochromes
NO peptidoglycan detected in 1 stage of life cycle
Developmental cycle of Chlamydia
1) EB (elementary body= non-replicating;infections; adapted for extracellular survival) taken into host cell by phagocytosis
2) Next 8 hrs EB reorganizes --> RB (reticulate body (non-infectious; replicating)
3) RB grows & divides by binary fission
4) 24-48 hr RB reorganizes -> EB
5) Completed: host cell liberates EB
(EB taken in--> (EB->RB) --> (RB binary fission)--> EB)
Are fungi eukaryotic? (ie have nucleus/nuclear membranes?)
Fungi are saprobes. What's a saprobe?
lives on dead or decaying organic matter
Yeast vs Molds
Yeast = unicellular; reproduce asexually via budding. form pseudohyphae

Molds: Multicellular (long filamentous HYPHAE, which intertwine to form MYCELIUM); Sexual or Asexual
Hyphae can be septate or aseptate. What's the difference?
Septate: partitioned
an intertwined mat of hyphae
2 portions:
1) Vegetative: attached to substrate/penetrates to obtain substrate
2) Reproductive - Aerial structures; Asexual reproduction propagules (conidia)
What is meant by Dimorphic Fungi?
exhibit 2 different forms (depending on Chemical & physical Factors)
1) Free-living State - Mycelial or Hyphal forms
2) Parasitic state: Yeast
How is Aspergillus an exception to Fungal Dimorphism?
ALWAYS in mycelial phase (ie free-living state, even when in deep tissue)
How is Torula an exception to fungal dimorphism?
ONLY in yeast phase
Fungal Architecture
Cell surface: glycocalyx
Cell wall
Cytoplasmic membrane
Nucleus (nuclear envelope, nucleolous, chromosomes
Cytoplasm - organelles (ER, golgi, 80S ribosomes)
Fungi don't have capsules, except for ____________
cryptococcus neoformans
Does fungi cell walls contain peptidoglycan?
Contains Chitin
What is found in a fungi's cell wall?
CHITIN (polymer of N-acetyl-D-glucosamine)
What is found in cytoplasmic membrane of fungi?
ERGOSTEROL (not cholesterol).
Fungal diseases: Mycoses
Cutaneous: invade keratinized & cutaneous tissue
Opportunistic infections: immunocompromised pts
Fungal features shared w Bacteria
microorganisms (not seen w naked eye)
all fungi grown axenically (without others) on artificial media
All fungi are aerobic or facultative
most are NOT capable of invading living tissue
Fungal features different from bacteria
All = Eukaryotic
80S ribosomes
Biochemically different & grow more slowly.