Symbiosis Flashcards
What are the 3 major types of symbiosis
Mutualism - Both organisms benefit from interaction
Commensalism - the microbe benefits from the interaction with no impact on host
Parasitism/competition - the microbe benefits at expense of host
What are metamonads
Found in the gut of a specific species of termite
Live in symbiosis with other bacteria
2 endosymbiotic bacteria which degrade cellulose which replaces mitochondria in metamonads
4 non-functioning flagella used for steering
3 ectosymbiotic bacteria provide motility
What are hemipteran insects
Several bacterial species are found in insects, including intracellular and extracellular bacteria, these are found in specialized cells called bacteriocytes which can aggregate to form organs called bacteriomes
What is symbiosis
any relationship or interaction between two dissimilar organisms
What is ectosymbiosis/endosymbiosis
A symbiont either living on the surface of a host or intracellularly
What is Legionella pneumophila
L. pneumophila is found in fresh water
It is a parasite of Amoebae that can also replicate
within alveolar macrophages.
What is Bdellovibrio bacteriovorus
B. bacteriovorus attacks Gram-negative bacteria
It invades the perisplams, feeds on host cell
What are Rhizobia
They live on plant roots and, through nodulation, fix atmospheric N2 to increase growth rate and yield
What are features of Rhizobia
Gram negative
Soil dwelling bacteria
Complex genome
Plasmids allow for nodulation and symbiotic interaction
How does nodulation occur
Bacterial attraction –> Production of Nod factors –> Root curling –> formation of infection threads –> Bacterial differentiation into bacteroids –> N2 fixation
How is bacteria attracted to the roots
Production of root exudates called flavonoids which attract bacteria
What are nod factors
Short oligosaccharides
What do nod factors do
They are perceived by the plant and trigger root curling (engulfs bacteria population)
What are infectious threads
Bacteria line the cell wall and enter the root through infection threads, bacteria multiply and progress in the root until they reach cortical cells which entrap the bacteria
What are the 2 fates of bacteria
Determinate nodules - longer, bacteria is alive, can resume growth if extracted
Indeterminate nodules - bacteria die, converted into differentiated cells which can fix nitrogen. Bacteria benefit (get carbs and AA in low O2 enviroment)
What are the differences between symbionts, parasisites organelles and viruses
Organelles are usually conserved across a wide range of organisms and are essential
Parasites are harmful for the organism they infect
Symbionts are beneficial organisms that live in association with another organism
What did metagenomics allow for
The identifying of thousands of bacterial species that cannot be grown in lab conditions
What is Mycoplasma genitalium
A large unusual symbiotic organism, causes an STD
What is the origin of small genomes in symbionts
Phylogenetic studies indicate that these organisms DO NOT have an independent origin
Genome size is the result of GENE LOSS
How is the mosaic biosynthetic pathway involved in AA biosynthesis
2 types of bacteria have a reduced genome
Produce AA mosaicly where the partners chip in to produce needed AA
What are intracellular pathogens considered as
Obligate parasites
What are symbiosomes
membrane vesicles that contain rhizobium cells
What can legumes use
ammonium and nitrates
