L13: archaeal diversity

what are the 2 major phyla of archaea

euryarchaeota + crenarchaeota (part of TACK superphyla)

what are most species adapted to

extreme conditions (extremophiles)

what does the genome of Asgard suggest about them

carry genomes specific to eukarya: eukaryotes could’ve evolved from them

what is the purpose of the S-layer

role in maintenance of cell environment + integrity (not a lot known)

do archaea have a cell wall

a very small amount do

if present, what is the cell wall made out

pseudomurein (equivalent to peptidoglycan in bacteria)

heteropolymer of disaccharide peptides

what are archaea cell walls resistant to

lysosomes + most antibiotics targeting peptidoglycan synthesis

what other unusual cell envelope structures are seen in archaea

archaellum (for mobility, moves by rotation)

cannulae (hollow tubes for nutrient transfer)

hooks (adhere to envelope on other cells)

describe the structure of archaeal cytoplasmic membrane

phospholipids containing isoprene’s rather than fatty acids

phospholipids are ether linked rather than ester

compare archaea membranes to bacterial ones

more stable + present as monolayers, bilayers, or mixture of both

describe archaeal chromosomal organisation

circular chromosomes (some have plasmids)

histones

multiple replication origins

encode polymerase B (shared with eukarya) + D (specific to archaea)

describe the difference between archaeal + bacterial gene expression

bacteria contain polymerase C while archaea contain polymerase B+D

describe features of transcription/RNA processing in archaea

single RNA pol similar to eukaryotic pol II

introns present

genes organised in operons

describe features of translation in archaea

coupled to transcription

several translation factors (like in eukarya)

70S ribosomes

list 3 major groups of archaea based on their physiology

(hyper)thermophiles

halophiles

methanogens

describe (hyper)thermophile archaea

include crenarchaeota + aeuryarchaota

high growth temp (80-120°C)

most require elemental sulphur to grow

often acidophiles (pH 1-3)

name a model (hyper)thermophile and describe its growth

acidianus infernus (crenrenarchaeota)

optimal growth 75°C + pH 2.5 - 3

grows anaerobically (prod. H₂S) or aerobically (prod. H₂SO₄)

or

thermococcus barossii

optimal growth 82°C + pH 2.5 - 3

grows anaerobically requiring sulfur

describe halophile archaea

mostly euryarchaeota

found in evaporating ponds, dead sea, + great salt lake

require up to 5M NaCl for growth

name a model halophile + describe its growth

halobacterium halobium

grows optimally at 75°C + pH 2.5 - 3

uses light as an energy source to secrete H+, gradient used to produce ATP

other transporters like halorhodopsin ensure ion transport

describe methanogen archaea

eurarchaeota

found in anaerobic environments

use acetate, formiate, or CO₂ as an electron acceptor

name a model methanogen + describe its growth

methanopyrus kandleri

grows at 105 - 115°C

or

methanobrevibacter smithii

prevalent species in human gut

contributes to removal of bacterial end products of fermentation