The microbial dimension of eukaryotic diversity L11 Flashcards
what kind of ancestors do all EUK have
microbial
what are the types of symbionts microbial eukaryotes can be
- Mutualists, commensals: members of the human/animal microbiota
- Parasites: can be important animal/human pathogens
give 5 types of microbial EUK
- Archaeplastida
- stramenopile, alveolata and rhizaria (SAR)
- excavata
- amoebozoa
- opisthokonta
describe structure of EUK
highly compartmentalised cells with endomembrane
describe phylogeny
evolutionary history of a group of organisms
- worked out by sequencing nucleotides or amnio acids
- some genes/proteins are distributed globally which allows us to study global phylogenies- tree of life
which organelles possess their own genome
chloroplast and mitochondria
what is the most widely used phylogenetic marker and describe it
small subunit ribosomal RNA (SSUrRNA) gene
- found in all cellular life forms
- 12S rRNA in M and C, 16S rRNA in pro and 18S rRNA in EUK
- the sequence is functionally constant- make up part of ribosome
- sequence changes slowly (conserved) allow cloning with degenerate primers (PCR) and generate informative alignments
Protein coding genes are increasingly used to complement SSUrRNA genes phylogenies
what does the M&C genome encode
- rRNAs and some proteins
(the vast majority of mitochondria proteins are encoded by the nuclear genome) - contain the necessary machinery for protein synthesis
how was the universal tree of life determined
comparative SSU rRNA gene sequence analysis
how are the 3 domains related to each other
- archaea’s genome is more like bacteria however, they are distinct from them
- Archaea have a common ancestor with EUK
which Eukarya did not have M
Trichomonads, Microsporidia, Diplomonads
- archeons
which bacteria did have M
proteobacteria
what does the archezoa hypothesis suggest
an archaeon with a nucleus engulfed a bacteria that became the mitochondria
what did 3 domain tree suggest
suggested that Archaea, Bacteria, and Eukaryotes represent primary domains of life
what did the 3 domain tree suggest
eukaryotes represent a secondary domain of life derived from a merger of two prokaryotes: an archaeal host and an alphaproteobacterial symbiont.
what is the significance of asgard archaea
EUK are very closely related to asgard archea
- they share many exclusive sequential patterns (ESPs) which code for proteins that regulate membrane trafficking
what are the 2 mitochondria like organelles and what are they found in
hydrogenosomes and mitosomes
found in archezoa called Trichomonads, Microsporidia and Giardia
describe hydrogenosomes
Produce hydrogen - H2
Produce ATP through substrate level phosphorylation
Some have a genome with mitochondrial signature
Nuclear genomes encode reduced fractions of mitochondrial proteins set
describe mitosomes
Reduced in size - can be < 100 nm in ø
No evidence for any capacity to produce ATP
No genome
Nuclear genomes encode reduced mitosomal /mitochondrial proteins set
is there support for any archezoa
no
- archezoa are meant to not have any mitochondria or derivatives of it- all found so far do
do we know if M or N came first
nope
- An archaeal cell could have been the host cell for the mitochondrial endosymbiont – rather than a eukaryote
when was chloroplast acquired
we know if was acquired after M and N
- engulfing of photosynthetic bacterium
describe the acquisition of chloroplast
- primary endosymbiosis creating glaucophytes, red algae and green algae- Archaeplastida
- secondary endosymbiosis
- engulfing of the algae, then transfer of genome
- red algae engulfing result in SAR:
Stramenopiles & Alveolates
- green algae results in Excavata
what are the two different types of parasites
- mucosal
- insect dependant
- extra or intra cellular
give type of protozoan, the disease it causes and how it is transmitted
- cryptosporidium species- diarrhea, water- borne
- plasmodium species- malaria, febrile disease, mosquitoes
- toxoplasma gondii- birth defects or encephalitis, undercooked meat
- trichomonas vaginalis- inflammation of urogenital track, STD’s
describe extra cellular parasite
Extracellular parasites thrive on and in tissues without entering their host cells (e.g. mucosal surfaces)
- Trichomonas
describe intra cellular parasite
Intracellular parasites need to penetrate their host cells to complete their life cycle
- They have developed specific means to invade their host cells without killing them and can exploit nutrients from within their host cells
- Microsporidia, Cryptosporidium
give 3 different intracellular microbial parasites and how they enter host
Apicomplexan
- Apical organ orchestrating moving junction mediated entry
Kinetoplastids
- Lysosome mediated entry
- Phagocytosis
Microsporidia
- Polar tube mediated entry
- In combination with endocytosis and/or phagocytosis?
what does understanding the genome of parasitic microbial EUK allow
Broaden our understanding of eukaryote genomic diversity
- Parasites are distributed across the diversity of eukaryotes
- Genome sequences of parasites led so far to many surprising findings, challenging our knowledge on eukaryotes
Important data source to discover and study traits underlying host-parasites interactions
- Surface and secreted molecules mediating interactions with host tissues – virulence factors
- Vaccine and diagnostic developments, identification of potential drug targets
why are the number of open reading frames in parasitic microbial EUK less than that in humans
Became much simpler as they exploit being inside the host- don’t need to make proteins, just take it from host
what are opisthokonta
a broad group of eukaryotes, including both the animal and fungus kingdoms
give examples of opisthokonta
- Animals, metazoa
- Host many microbial species – they represent very good niches for microbes in general – e.g. the human microbiota - Choanoflagellates and Ichthyosporea
- Mostly marine species - Fungi and Microsporidia
- Important decomposers of dead animals and plants
- Form important mutualisitic interaction with plants
- Include members of the human microbiota
- Many are pathogenic species to animals and plants
- microspordia infect gut then spread to brain and muscle
describe Microsporidia
Worldwide distribution
Opportunistic pathogens common in AIDS – HIV positive – patients
The two most common microsporidia identified in humans:
Enterocytozoon bienusi
Encephalitozoon intestinalis
Oral-faecal route – zoonotic origins (contacts with pets, farm animals, contaminated water, food,…)
Have mitosomes (reduce mitochondria without a genome)
describe Microsporidia life cycle
- spore has polar tube that is inserted into host (mainly animals)
- how it s infected - only replicated inside host
- intracellular parasite - spores formed and released
- Zoonotic origins for many, if not most, microsporidia infecting humans
3.
describe Stramenopiles
Many free-living species
Diatoms (a type of algae)
Some are symbiontes/parasites:
- Oomycetes: Phytophtora, plant pathogen (Irish potato famine), Blastocystis (animal and human gut-
commensal/mutualist?)
describe Alveolates
Dinoflagellates (mostly free-living)
Ciliates (mostly free-living and some parasitic forms)
Apicomplexa (exclusively parasitic)
- Parasites of animals and humans: e.g. Plasmodium falciparum, Toxoplasma gondii and Cryptosporidium hominis
how is Apicomplexa structured
apical organelles:
- dense granules, polar ring, microemers, rhoptries
- Active organelles used to infect host cell
nucleus, microtubles, apicoplast and mitochondria
how was apicoplast discovered in apicomplexa (which is a plastid)
1) Molecular data: Identification of an unexpected small genome: 35’000 bp.
2) Genome organization and
phylogeny linked it to plastids
3) Ultrastructural studies identify a new organelle, the apicoplast
- both M and A are conserved in apicomplexa so must be important in function
give examples of Apicomplexa infecting humans
- Plasmodium falciparum: human-anopheles mosquito life cycle, with mitochondria and apicoplast
- Toxoplasma gondii: cat-prey life cycle, common infections in humans – a zoonotic parasite, with mitochondrion and apicoplast
- Cryptosporidium parvum, C. hominis: only one host required, human or animal hosts (e.g. cow) – often a zoonotic parasite, with mitosomes and no apicoplast
give a type of Apicomplexa
Toxoplasma gondii
- Thought to cause benign disease in immuno-competent adults
Congenital transmission
AIDS associated
- With mitochondria and apicoplast with organellar genomes
what are the definitive and intermediate host of toxoplasma
D: felines
- Adult forms
- Sexual reproduction
I: birds and mammals
- Immature forms
- Asexual reproduction
Tissue cyst forming coccidia
what is the life cycle of toxoplasma
Parasite develops via sexual reproduction in cat forming oocysts in poo- ends up in mice
Infects gut of mouse and spreads to brain changing behaviour of mouse so its less likely to react to smell of cat so increases chance parasite will go back into to cat
Toxoplasma can also infect humans- can cause damage to foetus
We get toxoplasma via undercooked meat (if it is infected)
give another example of Apicomplexa
Cryptosporidium
-Worldwide distribution
Two species infecting humans
C. parvum: cattle and other mammals – zoonotic origins
C. hominis: only humans
- Typically, self-limiting diarrhea in immuno-competent persons
Profuse, watery diarrhea associated with immunodeficiencies – e.g. AIDS (life threatening)
do Cryptosporidium have M or A
reduced mitochondria, mitosomes (without a genome) and lost the apicoplast all together
give examples of The Excavata
- Parabasalia
Mainly obligate symbionts and include parasitic forms
Found in invertebrates, birds and mammals
Anaerobes, possess hydrogenosomes: e.g. Trichomonas spp. - Diplomonada
Many are host dependent and include parasitic forms
Anaerobes, possess hydrogenosomes or mitosomes: e.g. Giardia spp. - Euglenozoa
Free-living and parasitic forms
Kinetoplastids, parasites: e.g Trypanosoma spp. & Leishmania spp.
Some possess secondary plastids (e.g. free living Euglena spp.)
Somme possess complex mitochondrial genomes – kinetoplasts ~10-20% of total DNA present in a cell
describe Parabasalia: Trichomonas vaginalis
The most common sexually transmitted cellular pathogen
Can be very common in resource-limited conditions
Strongly associated with HIV and Mycoplasma
Linked with prenatal and post-natal complications
Positively correlated with cervical, and possibly aggressive/lethal prostate, cancers
what do Trichomonas vaginalis possess
hydrogenosomes
(modified M without genome)
what does trichomonas vaginalis cause
inflammation of urogenital tract if interacts with T. vaginalis viruses
- TVV dependent inflammation
Boosting of HIV transmission
- TV induced dysbiosis (BV)
Mycoplasma transmission
