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.
What does endosymbiotic theory suggest?
Mitochondria, plastids and hydrogenosomes evolved as symbiosis within other cells.
What does the hydrogen hypothesis suggest?
The endosymbiont was a hydrogen-releasing anaerobic bacteria within a hydrogen requiring chemosynthetic archaeon.
What is plastid endosymbiosis?
Evolutionary process in which a host cell gains the ability to photosynthesize from a guest cell.
What is bioluminescence an example of?
Symbiosis.
How is bioluminescence created?
Some animals produce their own, others have photophores, organs with cultures of luminescent bacteria. pg. 135
What are archeons?
Prokaryotes that have a cell wall lacking the sugar-amino acid of bacterial cell walls.
How are the lipids different in archaeons than bacteria?
They are related to the need to stabilize the membranes under extreme environmental conditions.
What does the domain archaea contain?
Photosynthetic, chemosynthetic, and heterotrophic organisms.
What are most archaeons?
Methanogens.
What are methanogens?
Anaerobic organisms that live in environments rich in organic matter which is metabolized for energy, with methane as a waste product.
What are halobacteria?
Example of archaeons, aerobic heterotrophs that can capture light for ATP production.
What are halophiles known as?
“salt-lovers”
When there is a shortage of oxygen, how do halobacteria survive?
Use light energy to produce enough ATP to survive.
What are hypothermophiles?
Archaeons that are known to survive in temperatures exceeding 100 degrees.
What is the unique method of digesting that eukaryotic cells perform?
Phagocytosis, inward building of the cell membrane to form a vacuole that encloses a particle.
Which domain are fungi within?
Eukarya.
What are fungi cell walls made of?
Chitin.
What do filamentous fungi grow into?
Long filaments called hyphae composed of many cells.
What are the mycelium?
What the branching of hyphae produces.
How do fungi produce energy?
They are heterotrophic, aerobic decomposers that recycle organic material, like most bacteria.
What is the most significant molecule that fungi can digest?
Lignin, a component of wood that allows it to reach fibres of cellulose.
What is glycogen?
A storage carbohydrate.
What are the 4 phyla in the kingdom fungi?
Basidiomycota, chytridomycota, zygomycota and ascomycota
What does growth of hyphae require?
Taking in water across the cell membrane.
What is much of the cellular activity of fungi directed towards?
Ridding cells of excess sodium.
Which marine fungi have the highest diversity?
Those that live in or on wood.
Which marine fungi have the second highest diversity?
Those that inhabit coastal salt marshes of temperate zones.
How do marine yeasts reproduce?
Asexually through budding.
What is budding?
A mitosis that produces daughter cells of unequal size
How do filamentous marine fungi reproduce?
Asexually through producing conidospores that are released and carried away.
How do filamentous marine ascomycotes reproduce?
Sexually, by producing an ascocarp. A zygote nucleus is formed, developed into eight cells that mature into ascospores.
What are lichens?
Mutualistic associations between a fungus and an alga. The fungus provides attachment, the alga organic matter.
What are stramenopiles?
A diverse group of eukaryotic organisms.
What unites the group of stramenopiles?
The nature of the two flagella they have. One has a short simple form, the second is longer with many hair-like filaments called mastigonemes.
What do the flagella of stramenopiles do?
The shorter senses lights and pushes the cell, the second is feathery and pulls the cell forward.
What does heterokont mean?
There are two different forms of flagella.
How do stamenopiles produce energy?
Can be nonphotosynthetic or photosynthetic
What are ochrophytes?
Photosynthetic stramenopiles, usually contain the brown pigment.
What are diatoms?
Members of phytoplankton and benthic communities. Abundant in high latitudes.
What do benthic habitats include?
Soft sediments.
How do diatoms store their food reserves?
As lipids and laminarin, making them more buoyant.
What is unique about diatoms?
The cell wall, called a frustule, that is composed of organic pectin and silica mineral components.
What is each half of the frustule called?
Valve. One is larger than the other.
What does the surface of a frustule have?
pores, knobs, grooves, spines etc.
What 2 shapes do diatoms occur in?
Radially symmetrical, or centric, valves and bilaterally symmetrical, pennate, valves.
which diatom shape is more typical of the benthos?
Pennate.
How do some benthic diatoms move?
Secretion of mucilage from pores
How do diatoms reproduce?
Asexually by fission.
What happens to the daughter cells of diatoms during reproduction?
They inherit only one of the two valves from the parent, so it completes its frustule by secreting a new smaller valve inside the inherited one. The daughter with the larger valve can grow to the same size as the parent, but the other is limited. Average cell size then decreases over generations.
What happens when the cell size of a diatom reaches 50% of the maximum?
Forms an auxospore that increases the volume of the cell and secretes a normal sized frustule. This is then followed by sexual reproduction.
What happens to diatoms under poor conditions?
Form resting spores, the frustule thickens and cytoplasm becomes denser, making it sink.
Being without what will limit diatoms?
Silica.
What are silicoflagellates?
A type of ochrophyte abundant in cold waters that have basket shaped silica skeletons.
What are labyrinthomorphs?
Stramenopiles that lack plastids and have osmotrophic nutrition. Cells secrete mucous coating so they can move.
What are haptophytes?
Includes mainly photosynthetic organisms.
What are the flagella in haptophytes?
Two similar flagella for locomotion and a unique structure, the haptonema.
What is the haptonema?
Arises from the cell surface between two flagella. Catches food on its surface and transfers it to the posterior.
What are the majority of living haptophytes?
Coccolithophores.
What are coccolithophores?
Species with calcium carbonate scales produced internally within membranous vesicles and transported to exterior.
Coccolithophores account for what percentage of carbonate production in the sea?
40%
What are alveolates?
Cells with membranous sacs beneath their membranes. they are grouped into dinoflagellates and cilates.
What are dinoflagellates?
Globular single-celled organisms with 2 flagella that lie in grooves on the cell surface.
What are some unique features of dinoflagellates?
Contain a decay-resistant chemical, some are bioluminescent.
What is the dinoflagellate structure?
Heterokont, arising from pores. A shorter flagellum encircles it which makes it spin, and a longer one trails in n a longitudinal groove which powers forward motion.
If dinoflagellates are armoured what is different?
Thin cellulose plates are in multiple layers very thick.
How do dinoflagellates obtain food?
Store food as starch of the same composition as green plants. Mixotrophic, use osmotrophy or phagotrophy rather than photosynthesis.
How do dinoflagellates reproduce?
Asexually by fission. If sexually in some species, it is by fusion of gametes.
What is the ecological role of dinoflagellates?
Major part of the phytoplankton providing food to many animals.
What are harmful algal blooms?
Dinoflagellates are responsible for them, as their population explodes, produce toxins harmful to nervous system.
What are ciliates?
Protozoans that bear cilia for locomotion and food.
What are distinctive features of ciliates?
Found in tufts or rows, possession of 2 nucleus a micro and macro.
How do ciliates reproduce?
Asexually by fission, sexually by conjugation.
What is the ecological role of ciliates?
Transfer production from bacteria to higher levels in the food chain.
What are choanoflagellates?
Phylum of flagellated cells that are related to animals, with a single extending flagella surrounded by microvilli.
What are amoeboid protozoans?
Have an organelle called a pseudopod that can change shape. Heterotrophs
Do amoeboid protozoans have a cell membrane?
Some, although most have a shell of test.
What is a test?
Externally secreted organic membrane that is covered with foreign particles.
What are foraminiferans?
Amoeboid protozoans having branches pseudopods that form elaborate structures, reticulopods, to snare prey. or crawl. Some harbour symbionts to get nutrients.
How do forminiferans reporduce?
Sexually and asexually
What are radiolarians?
Highly diverse class of zooplankton named for the long pseudopods they have.
Where do radiolarians live?
In the photic zone.
