Protists (Lec 5) PDF

Ciliates • Covered in cilia • Most developed protozoan • Cytostome (mouth) • Cytoproct (anus) • Two type of nucleus • Macronucleus • Micronuclei Four Eukaryote Supergroups Excavata SAR Archaeplastida Unikonta ‘Protists’ in yellow NB You do not need to learn this map! Cilia Contractile vacuole...

Ciliates • Covered in cilia • Most developed protozoan • Cytostome (mouth) • Cytoproct (anus) • Two type of nucleus • Macronucleus • Micronuclei Four Eukaryote Supergroups Excavata SAR Archaeplastida Unikonta ‘Protists’ in yellow NB You do not need to learn this map! Cilia Contractile vacuole Micronuclei Macronucleus Food vacuole Cytostome (mouth) Membranelles (stiffer cilia) Cytoproct (anus) Cilia • Microtubule-based hair-like organelles Free-swimming Usually attached (‘sessile’) Cilia Cross section view • Motile cilia • 9+2, dynein motor protein • Ciliates • Humans (bronchial and oviduct epithelium) • Non-motile cilium • 9+0, no dynein motor protein • ‘Primary cilium’ on all human cells Cilia • Used for movement • Go back and forward • Some fuse to form ‘cirri’ • Very important for feeding Euplotes • Direct prey towards the mouth area (‘cytostome’) • Cytostome contains stiffer cilia (‘membranelles’) • Sieve - correct sized prey enter food vacuoles • ‘Filter feeding’ CYTOSTOME in free swimming ciliates (swim and feed) CYTOSTOME in attached ciliates (more difficult to locate) Vorticella Prey drawn towards cell Vortex at cell mouth Very large feeding currents No swimming, so cilia only used for feeding (extensive feeding currents) Exception to rule - Suctorian ciliates • Numerous microtubule tentacles • Each tentacle ends with a cytostome • Extrusomes – secrete toxins • Dissolve prey contents and suck out!! • ‘Raptorial feeding’ Prodiscophrya https://youtu.be/o_8OK9afr9Y Mixotrophic ciliates • Do not contain their own plastids • Acquire photoautotrophic ability two ways • Organellar mixotrophy and Cellular mixotrophy • e.g. Strombidium Euplotes Ciliate reproduction • Asexual reproduction • Transverse ‘binary fission’ • Involves mitosis • Sexual reproduction • Conjugation • Involves meiosis and mitosis • Micronuclei swap • Allows for genetic variation Sexual Campbell page 661 Cellular diversity Vorticella Stentor Cellular diversity – some exist in a ‘lorica’ Vaginicola Stichotricha ANAEROBIC CILIATES – The ‘Sulphur ciliates’ Pyruvate Hydrogenosomes H2, Acetate, CO2 Methane Methanogenic bacteria Methanogenic bacteria: Domain Archaea Metopus containing methanogenic endosymbionts – B, visualised under UV light (fluorescent coenzyme F420) Flagellates • Posses flagellum/flagella (9+2) • Not backwards and forwards • In humans - sperm • Posses macronucleus only • Longitudinal ‘binary fission’ • Mainly aerobic • Feed by Heterotrophy, Photoautotrophy & Mixotrophy Four Eukaryote Supergroups Excavata SAR Archaeplastida Unikonta Flagellates are in all 4 supergroups!! Heterotrophic Flagellates • Also called ‘Zooflagellates’ • Most are aerobic • Consume pre-formed organic carbon • Prey digestion: • Organic carbon (sugars) to inorganic carbon (CO2) • Use flagella for movement and catching prey • Raptorial feeding • Filter feeding Naked and hispid (hairy) flagellum Naked flagellum Direction of swimming Hipsid flagellum Direction of swimming Raptorial feeding (with a hispid flagellum) • Create feeding currents due to flagellar movement • Prey is drawn towards the base of the flagellum • Ingested via cytoplasmic extensions (pseudopodia) Direction of swimming Raptorial feeding (with a naked flagellum) • Create feeding currents due to flagellar movement • Less contact with the base of the flagellum • Less efficient capture of prey Direction of swimming Increasing prey capture (with a naked flagellum) Increasing prey capture (with a naked flagellum) Filter feeding • Collar of tentacles (microvilli) • Contain actin - contractile Choanoflagellates • Only group with a collar of tentacles • All have a single naked flagellum • Attach to surface (by means of a stalk) • More closely related to animals than other protists!! Monosiga Four Eukaryote Supergroups Excavata SAR Archaeplastida Unikonta ‘Protists’ in yellow NB You do not need to learn this map! Cross section of a sponge Sponge Campbell pages 729-730 Silica lorica in marine choanoflagellates only Diaphanoeca Stephanoeca Biomimetic engineering Photoautotrophic Flagellates • Also called ‘Phytoflagellates’ • Own plastids – green or golden • Photosynthesise • 6CO2 + 12H2O = C6H12O6 + 6H2O + 6O2 • Inorganic carbon (CO2) to organic carbon (glucose) • All are aerobic • Use flagella for movement towards light and nutrients Euglena (photoreception) Eyespot/Stigma: Organelle containing carotenoid lipid globules. Shading device for photoreceptor to detect direction of light. (Paraflagellar Body) In Dinoflagellates only… 2nd flagellum around the waist Ceratium Solitary cells Chlamydomonas Mallomonas Colonies (NOT ‘multicellular’) Synura Volvox Mixotrophic Flagellates • Phytoflagellates that eat (best of both worlds) • ‘Constitutive mixotrophy’- have their own plastids • all are aerobic • Can also ingest prey – raptorial feeding • Use flagella for movement and prey capture • One type of feeding is normally over-riding • Depends on the genus and light climate Mixotrophic Flagellates • Some exist as solitary cells • Ochromonas • Few plastids • Prefers to feed on prey • Some form colonies • Dinobryon • Plastids dominate cell • Prefers to photosynthesise THE PRACTICAL DATA Feeding in the mixotrophic Dinobryon divergens Feed with prey at Time zero Determine prey/cell after 30 min EFFECT OF LIGHT REGIME (HIGH/LOW) AND TEMPERATURE ON FEEDING AND PHOTOSYNTHESIS