Microbes Flashcards
What are microbes?
Organisms invisible to the naked eye.
Outside of the host cell, what is a virus particle called?
Virion.
What is a virion composed of?
Nucleic acid core surrounded by a capsid, or coat of protein.
What is an envelope?
A membrane derived from the hosts nuclear or cell membrane.
What are the three common shapes that viruses occur in?
Icosahedral, helical and binal.
What are the two categories of life cycles recognised in viruses?
Lytic and lysogenic.
What is the lytic cycle?
Rapid cycle of infection, replication of viral nucleic acids/proteins, assembly of virions and rupture release.
What is the lysogenic cycle?
Viral nucleic acid is inserted into the host and can reside there through a lot of division before becoming lytic.
What are most marine planktonic viruses?
Icosahedral or binal bacteriophages with DNA and lytic cycles.
What do viruses control in plankton communities?
Population.
What can defeat viruses?
Light entering the ocean, being absorbed onto suspended particles.
How are bacteria cells organised?
Prokaryotic, so lacking nuclei and other membrane-bound organelles. Have one single chromosome of DNA.
How do bacteria reproduce?
Asexually using binary fission.
What is binary fission?
A cell’s genetic material is copied, and the cell splits into two equal daughter cells. Each then rapidly grows, and repeats.
How are marine bacteria shaped?
This varies. Most are rod shaped or bacillus, can be spherical or coccus, can also be corkscrewed or spirillum.
What are amoeboid protozoa?
Organisms that have a pseudopod, an extension of the cells surface that can change shape. Used for locomotion and food catching.
What is benthic?
On a surface or the bottom.
What is pelagic?
In the ocean.
How to bacteria acquire nutrients?
Some are primary producers (autotrophs), using either the sun or chemicals. Some are heterotrophic which use absorption.
What are heterotrophic bacteria?
Obtain nutrients by absorption across the cell membranes, called osmotrophic. If they encounter something too big, they break it down.
What is a critical aspect of bacterial metabolism?
Ability of some groups to break the strong bond of molecular nitrogen.
What are cyanobacteria?
Photosynthetic bacteria found in environments high in dissolved oxygen.
What are the primary photosynthetic pigments in cyanobacteria?
Chlorophyll a and b.
What are the accessory photosynthetic pigments?
Carotenoids and phycobilins.
What do carotenoids do?
Impart a yellow colour.
What do phycobilins do?
The reddish and blue pigments.
What is chromatic adaption?
When concentrations of pigments change as the quality of sea light changes.
What are photoprotective pigments?
Pigments containing complex chemicals in primary producers that reduce potential harm to chlorophylls by light.
What do cyanobacteria secrete?
Mucilage
What are the associations that cyanobacteria form?
Stromatolites
What are stromatolites?
Mounds of microbes that trap sediment and precipitate materials in shallow tropical seas.
Where do stromatolites occur?
Bahamas and Australia.
Why do stromatolites only occur in certain locations?
Because they are very salty so their competitors are absent.
What are other examples of photosynthetic bacteria?
Green and purple sulfur, nonsulfur bacteria.
What is different about other photosynthetic bacteria?
They are anaerobic and dont produce oxygen as a byproduct of photosynthesis.
How do sulfur and nonsulfur bacteria that are anaerobic get energy?
Splitting of hydrogen sulfide which produces sulfate and small organic materials.
What are chemosynthetic bacteria?
Bacteria that use energy derived from chemical reactions.
What are heterotrophic bacteria?
Use available organic matter to obtain energy for synthesis of their own compounds and metabolism. They are decomposers.
Which bacteria release exoenzymes with the capacity to digest natural molecules otherwise resistant to decay?
Heterotrophic.
What does the association of bacteria and particles in the water column aid in?
Consolidation, lithification and sedimentation.
What is consolidation?
When sticky surfaces cause adjacent particles to adhere to each other.
What is lithification?
Minerals precipitating and forming a cement between particles.
What is sedimentation?
Particles settle.
What is nitrogen fixation?
Process that adds new, usable nitrogen to the sea by converting molecular nitrogen to ammonium ion.
What is nitrogen required for in the sea?
Forming amino acids, nucleotides.
Why may there be a deficit of nitrogen at surface waters?
Rapid uptake by primary producers and loss in settling particles.
Why are some cyanobacteria capable of fixing nitrogen?
They have an enzyme, nitrogenase, capable of breaking the strong molecular bonds that make up nitrogen gas.
What environment should nitrogen fixation take place in?
Anaerobic.
Where does nitrogen fixation take place in many bacteria?
A heterocyst.
What is a heterocyst?
A thick-walled, mucilage coated cell in which photosynthesis is altered to prevent the release of oxygen.
What is nitrification?
Bacterial conversion of ammonium to nitrate and nitrate ions so that cyanobacteria can use it.
What is symbiosis?
Two different organisms form a very close association with each other.
Which symbiotic relationships have the longest history?
Mitochondria, chloroplasts, others of the domain eukarya.