Free Living Amoebae Flashcards
free living amoebae all belong in this group
Sarcodina
free living amoebae genera that are potentially pathogenic to humans + other vertebrates
Acanthamoeba
Naegleria
Balamuthia
Sappinia
Hartmannella
amphizoic
amoebae’s ability to exist within a host or in environment as free-living forms
T or F. Most free-living amoebaes are bacteriophagous inhabitants of soil, water, and sewage
T
most amoebae exist in two basic forms
trophozoite
cyst
some amoebae are diphasic:
ameboid (binary fission)
flagellated stage
when does amoebae encystment occurs
under adverse environmental conditions and allow for survival outside host
amoebic trophozoites
pseudopods
adhesion essential for locomotion and feeding
movement enhanced by higher temps (30C)
amoebastomes/”food cups” = cytoplasmic extension
- ingestion of bacteria and cell debris
- attachment to surfaces
*NO correlation w pathogenicity
the flagellated tage of amebae
- cell changes shape = synthesizes new flagellar apparatus
> more rigid cell, pear-shaped, sturdy shape, faster movement - induced by nutritional deprivation, temp or osmotic shock
- lasts from 2 to several hrs
cyst stage of amoebae
- environmentally hardy form
- mucopolysaccharide double wall, resistant to biocides
- Ostioles (pores) sealed by mucus plugs
- cysts not formed in tissue, left behind when trophozoite emerge
ostioles
pores that allow communication that allow communication inside and outside of amoeboid cyst
not formed in tissue; left behind when trophozoites emerge
when trophozoites come out of cyst, they squeeze through this which leave intact cyst = easily seen in microscope
Naegleria fowleri
diphasic amoeba
- exist in amoeboid and flagellate form (2 to several hours)
- agent of amoebic encephalitis
lifecycl of Naegleeri fowleri
invasion via nasal passages on contact w water (ex: water slides without plugging nose)
> amoebae travel along olf nerves
> cribriform plate to brain
INHALING infested water is how you get infected; ingestion of water does nothing
virulence of Naegleria depends on:
- Nfa1 protein (mediates amebic attachment to target cells; first step to cell invasion)
- Feeding cups (help directly phagocytose the brain cells).
- Nitric oxide production
- Pore-forming proteins.
- Cytolytic molecules like cysteine proteases, phospholipases, and phospholipolytic enzymes
epidemiology of N. fowlerii
- ubiquitous = freshwater lakes, hot water springs, poorly chlorinated pools (NOT in seawater)
- worldwide
- growth enhancement at high temps (42C); thermophilic organism
- protection = calination and chlorination (cysts more fragile than Acanthamoeba)