amoebae

features of amoebae

one macronucleus, mostly aerobic, most heterotrophic, some mixotrophic, asexual reproduction with no specific fission plane, some move, some don't

naked amoebae features

move by cytoplasmic streaming, held together by cytoplasmic streaming, produce pseudopodia for movement, raptorial feeding, no specific location for ingestion

pseudopodia

false feet

raptorial feeding

feeding by direct interception of prey

trophozoites - naked amoebae

feeding form

cysts

resting stage for unfavorable conditions

floating form

non feeding form, stiffened pseudopodia for dispersal to help it float, happens when it can't find a surface to attach to

shelled amoebae

enclosed in a test (shell) which can be made of anything

intrashellular cytoplasm within test, projects extrashellular cytoplasm for feeding/moving, raptorial/diffusion feeding

testate amoebae

freshwater, marine and terrestrial - raptorial feeding

foraminiferans

marine, diffusion feeding - stationary predator captures prey with sticky extrashellular cytoplasm (axopodia)

radiolarians

marine, silica tests, diffusion feeding

heliozoans

freshwater, silica tests, diffusion feeding

positive ecological impact

base of every food chain, keep bacterial protists healthy, important in nutrient cycling

microbial loop

co2 leaks into water - dissolved organic carbon, consumed by bacteria, bacteria consumed by protozoa, metazoa predate these, this keeps bacteria in log phase

protist CNP ration

50:10:1

remineralisation

protists have to maintain cellular CNP ratio, they are always losing carbon so they pump out N and P to maintain ratio, this is released as NH4 and PO4 which feeds bacteria

negative ecological impact

allow the evolution of new pathogenic bacteria, become a reservoir for pathogenic bacteria

how do they allow evolution of pathogenic bacteria

amoebae and macrophages are very similar so bacteria practice evading digestion in amoebae

how do bacteria avoid digestion

change surface antigens, produce very thick capsules to hide antigens, avoid fusion of phagosome with lysosome, then either divide in phagosome or cytoplasm

acanthamoeba

eye infection - keratitis, water reservoir, transport - dirty contact lenses

naegleria fowleri

brain infection - primary amoebic meningoencephalitis, reservoir is warm water, transport - flagellate swims up nose

trichomonas vaginilis

STD - trichomoniasis, reservoir is humans, transmission through sexual intercourse

leishmania mexicana

blood/tissue infection - leishmaniasis, reservoir is dogs, transmission by sand fly vector