Microorganisms Flashcards
Essential features of virus
- outer protein coat
- inner coiled genome
- genome is either DNA or RNA
- lack ribosomes so cannot reproduce themselves
- proteins are synthesised of host ribosomes
Capsid
- made from repeated subunits called capsomeres
- capsomeres self assemble in geometrical way
- coding for single unit minimises genome size
- simplest structures are icosahedral and helical
- must contain surface exposed viral proteins on surface to recognise host receptor
Enveloped virus
- viruses released from the cell by budding are usually surrounded by membrane derived from the host membrane
Non-enveloped virus
- viruses released by lysis are usually naked protein capsids
Viral life cycle
- virus binds to host cell via receptor
- virus is taken up by cell and capsid disassembles
- replication proteins produced in host ribosomes
- viral genome is replicated, capsid reassembles, new virus produced
- virus released through cell membrane or lysis
Bacteriophage
- virus that infect bacteria
- have syringe like tail to inject genomes into host cell
Lysis
- phage DNA is replicated
- phage proteins synthesised
- progeny phage are assembled
- cell breaks open
- mature phage released
Lysogeny
- recombination takes place between phage DNA and bacterial DNA
- phsge DNA is replicated with bacterial DNA and transmitted to bacterial progeny
+ sense RNA
every viral genome must be transcribed into mRNA+ for virus proteins to be made by the host cell
Stromatolites
- layered microbial communities
- found in shallow warm water
Prokaryote shape
- coccodial eg. Streptococcus
- bacterial rods eg. E.coli
- helical bacteria that produces anibiotics eg. Streptomycetes
- small square archaon eg. Haloquadratum walsbyi
Bacterial cell
- DNA is contained in circular chromosome
- often have small circles of additional DNA called plasmids
- have cell wall and plasma membrane made of peptidoglycan
Gram staining
- used in bacterial ID
Gram positive
- purple
- thick layer of peptidoglycan
- can form endospores, which are specialised for survival and dispersal
Gram negative
- pink
- thin layer of peptidoglycan
- has outer membrane with polysaccharide chains
Growth of bacterial cells
- swimming cells attracted to food bearing surfaces
- cells settle on surface and move in large groups until suitable location is found
- cells attach firmly to surface and form microcolony
colonies form biofilm
cells on top of biofilm are released, grow flagella, and find new location
DNA transfer by conjugation
- DNA from donor cell transferred to adjacent recipient cell
- pilus tethers donor to recipient and brings cells together
- DNA passes through small opening when cells are alligned
DNA transfer through transformation
- DNA released into environment by dead cells
- DNA taken up by recipient cell
DNA transfer though transduction
- DNA is transferred from donor cell to recipient by a virus
DNA transfer of bacteria to plants
- bacteria enter plant through wound
- section of Ti plasmid is inserted to plant genome
- Ti genes cause host cell to divide and form tumour
- compounds that bacteria can metabolise are produced
Isolates
- what bacteria are initially named as
- group of similar isolates forms a species
Archaea
- known as Archaeabacteria
- organisation is similar to bacteria
- cell wall is never made from peptidoglycan
ribosomes and polymerases are simpler versions of eukaryotes - unique cell membranes and metabolic pathways
Extreme helophiles
- aerobic
- grows in saturated salt solution
Methanogens
- anaerobic
- produce methane
- distributed in oxygen free environments
Thermoacidophiles
- grow at temperatures above 80
- usually found in high acidic conditions
- sulfur based metabolism
Microbiome
- microbial community found in a particular environment
- can be characterised through sequencing bulk samples (metagenomics)
Contents of Eukaryotic cell
- cytoskeleton
- nuclear membrane
- nucleus
- endoplasmic reticulum
- golgi apparatus
- mitochondrion
- plasma membrane
Cytoskeleton
- enables cells to change shape and remodel quickly
Nuclear membrane
- separates transcription and translation
- vesicles budding off from membranes transport materials into the cell (endocytosis) and release materials out of the cell (exocytosis)
Mitochondria
- surrounded by double membrane
- inner membrane folded into cristae to increase surface area
- small molecules transported from cytoplasm to matrix and oxidised to CO2
- ADP transferred from cytoplasm to matrix, phosphorylated, and released back to cytoplasm
Origin of mitochondria
- mitochondria are said to be derived from Rickettsia-like parasites
- are bacterial in origin
- have own small chromosome
- ribosome sequence resembles those in Rickettsia
- Rickettsia take up ATP, use energy, export ADP (opposite from mitochondria)
Origin of Eukaryotes from Prokaryotes
- eukaryotic cells evolved from ancestral archaeon and later incorporated proteobacterial cell which became the mitochondria
- supported by discovery of Lokiarchaeota, which resembles eukaryotic cell without mitochondria
Excavates
- contains many parasites of human pathogens
- eg. trypanosomes and euglena
Stramenopiles, Alveolates, Rhizarians
- stamenopiles include diatoms
- have silica shell call frostrule
Ciliates
- alveolate
- large complex cells
- often have mouth and gullet
- surface covered in short flagella which beat in unison (cilia)
- two nuclei per cell; macronucleus for transcription; micronucleus for reproduction
- includes paramecium
Apicomplexans
- alveolate
- parasitic
- complex multi host lifecycle
- eg. plasmodium
Archaeplastids
- are plants
Amoebozoans
- cytoskeleton allows eukaryotic cell to engulf another
- include Myxomycetes, radiolarians, foraminiferns, dicteyostelids
Myxomycetes
- haploid amoebas engulf smaller prey
- fuse to form diploid structure, grows into giant plasmodium and forms many nuclei
- conditions deteriorate, fruiting bodies form to create haploid spores for dispersal
Radiolarians
- large aquatic silica skeleton
- long slender pseudopodia supported by microtubules
Foraminiferans
- calcium carbonate shell
- long slender pseudopodia which form mesh like network
Dicteyostelids
- haploid amoebas grow and reproduce as solitary organisms
- can mate to form diploid macrocyst, undergoes meiosis to produce haploid amoebas
- conditions deteriorate, pheromones released, amoebas join to form multicellular slug
- slug locates suitable location to produce fruiting bodies to make and disperse haploid spores
Steps of complex multicellularity evolution
- cells stick together by signalling to eachother
- gap junctions allow materials to be exchanged
- bulk flow, where vascular organs carry nutrients, water, blood etc.
Opisthokonts
- complex multicellularity evolved multiple times
- choanoflagellates, red algae, green algae, brown algae, fungal fruiting bodies, slime mould fruiting bodies
Fungi
- belong to opisthokonts, are heterotrophs
Hyphae
threads that form underground network called mycelium, which have many nuclei per cell
Chitrids
flagellated spores, cell wall made of chitin, some form mycelium, decomposers or parasites
Zygomycetes
simple moulds, haploid hyphae reproduce through haploid spores produced in sporangium, parasites of insects
- diploid cells undergo meiosis to form ascus with four ascospores
Basidiomycetes
largest most complex fungi, short lived haploid hyphae fuse to form dikaryotic hyphae called secondary mycelium
- reproduce by production of basidiocarps where nuclear fission and meiosis occur
Lichens
symbiosis between fungi and algae
Fungus like microbes
- have cell walls
- cylindrical hyphae forming branched mycelium
- reproduces by spores
- spores often swim
- cell walls not made from chitin
Fungus like organism examples
- opisthokonts - true fungi
Amoebozoans - myxomycetes and dictostelids
stramenopiles
Oomycetes
- spores are diploid
- zoospores germinate and form diploid mycelium
- sexual reproduction through gametes
Myxobacteria
- gram negative bacteria
- glide over surfaces in packs
- food is scarce, releases signals, aggregate and form fruiting body
