Lecture 3b- the microbial loop Flashcards
Explain the feeding of guild a bacteria in the context of algae
-algae fix inorganic carbon from the atmosphere, and relase this from their cells as dissolved organic carbon (DOC). this is then fed on via indirect feeding by guild a bacteria
what is the feeding of guild a bacteria an example of? define it
COMMEMSALISM- the waste of one organism is used by another
what is bacteria (eu/prokaryote?)? size
single cell prokaryotes lacking a nucleus and ranging from 0.2-2 micrometers in size
what are the two types of bacteria in terms of carbon acquisition?
heterotrophic or autotrophic
explain the feeding of heterotrophic bacteria
assimilate organic carbon in the form of poc of doc
explain the feeding habits of autotrophic bacteria
assimilate inorganic carbon via photosynthesis or chemotrophy
Give information on guild a bacteria (eg type of carbon utilised)
- the largest guild, AEROBIC bacteria
- utilize DOC for carbon and electrons
- are mineralisers and not decomposers, but technically break down organic carbon into co2 and water
what is the key genus of guild a bacteria?
pseudomonas
what is the relationship between guild a bacteria and algae?
mutualism
explain the relationship between guild a bacteria and algae
-algae produce DOC whih is indirectly fed on by guild a bacteria
guild a bacteria break this down and produce carbon dioxide, which is then utilized by the algae for photosynthesis
why is the relationship between algae and guild a bacteria not codependant?
carbon dioxide is not limiting within natural waters, so technically the algae don’t require guild a. Therefore its described as photocoperation
When is the relationship between bacterial biomass and algae biomass the strongest?
when there is no other source of doc within the water column. The relationship is often linear at this point.
what is the other source of DOC in waters? when is this most utilised?
humic substances that enter the water column . in locations where algae productivity is limited by light (due to a high proportion of humic substances blocking out the light) doc from humic substances become the prominent source.
what is humic material?
dead animal and plant material (POC) that is broken down into DOC by bacteria
finally, what are the three sources of DOC for guild a bacteria?
- algae
- decomposers
- humic substances
give information on guild b bacteria
- gliding/true decomposers.
- breakdown POC into DOC
- -found on sediment particles, rock surfaces, planktonic aggregatrs and faecla particles
what do guild b bacteria breakdown? (4 substances)
-cellulose, chitin,pectin,keratin
why are guild b bacteria true composers but guild a arent?
guild a breakdown DOC into co2 and water, but guild b breakdown POC to DOC
are heterotrophic protezoa predators or decomposers?
True predators, feed on other organisms
what do heterotrophic protezoa predate?
-Algae and guild a bacteria
describe heterotrphic protezoa (eg. eukaryotes, aerobic/anaerobic etc)
- eukaryotic
- anaerobic
what are the three types of heterotrophic protezoa?
- flagellates
- amoebae
- cilliates
what are the only two anaerobic protezoa?
-sulphur cilliates and one flagellate
describe naked ameoba (motion, attachment, feeding habit)
- latin name ameoba proteus
- move via cytoplasm streaming. this is done via pseodopodia
- can only move on the surface of substrates, and use pseudopods to catch non-motile prey
- known as feeding by rapotoral feeding
How do naked aemeboe feed?
Raptoral feeding
describe briefly what Pseudopodia is
where cytoplasm-filled parts of the cell membrane are able to temporarily change their form to move
where do testae amoebae live?
in the water column (pelagic)
what are testae amoebae enclosed in? give information on the two types
- they are enclosed in a shell of calcareous or siliceous material
- two groups: radalorians and foraminifera
how do testae amoebae catch food?
- they project heir intrashellular cytoplasm that catches prey that swims by
- once prey is caught, the cytoplasm is retracted back into the shell
what are the two types of feeding utilised by testae and naked amoebae?
- naked utilised raptoral feeding
- testae utilise diffusion feeding
describe the feeding patterns and movement etc of zooflagellates (heterotrophic flagellates)
- use “hairy” flagellums for feeding and swimming
- most efficent when attatched to a surface
- prey injested via pseudopods within the flagellum
explain loricas and zooflagellates
-zooflagellates produce loricas out of sillica strips and uses this to float in a basket (only in marine systems)
why are zooflagellates most effective when attatching to a surface/inside a lorica?
-they need to make currents for swimming and feeding. they can therefore focus on making the most effective currents for food acquisition
Describe cilliates
- how they swim
- prehistoric features
- nucleus
- the most diverse group of protezoa
- covered in cillia (hairs) used for swimming
- prehistoric mouths called CYTOSTOME and anus CYTOPROCT
- two types of nucleus: macronucleus and micronucleus
What happens to cilliate micronuclei in mating?
-micronuclei are transferred between cells in sex, leading to high diversity
explain the functional role of protezoa in marine environments (C:N:P ratio)
- they keep the C:N:P ratio strictly at 50:10:1
- this is done by pumping out inorganic N and P when carbon is lost in respiration (as this changes the ratio)
- their functional role is also to eat algae+ bacteria and provide food for invertebrates
how does the microbial loop appear in anaerobic environments?
- anaerobic bacteria serve as primary producers, and sulphur cilliates are the ONLY protezoa
describe guild F bacteria
- green and purple sulfur bacteria
- only exist in anaerobic environments, and carry ANAEROBIC PHOTOSYNTHESIS
- core genus: Chromatium
what type of light do guild F bacteria utilise? why?
-utilise far-red light, as “normal ligh” is often limiting at the bottom of lake environments (where anaerobic conditions are most commonly found)
what do guild f bacteria produce from photosynthesis?
-doc
what do guild f bacteria use in place of oxygen as their electron fixer?
-hydrogen sulfide
Describe guild E bacteria
- anaerobic
- use sulphate to fix electrons in respiration processes
- produce DOC
- also carry out anerobic respiration
Explain the relationship between guild E and guild F bacteria in the anaerobic environment
-guild F bacteria produce SO4, and guild E bacteria produce HS2. these are the substances that the other requires as their electron fixer, so subsequently they have a COMMENSALISM relationship.
why are guild E bacteria not limited by carbon
-DOC is produced in house by guild F, and it diffuses down by the aerobic layer
What type of bacteria carry out methanogenesis?
-Guild G bacteria
What is methanogenesis, where does it occur, and what bacteria do it?
- methanogenesis is the formation of methane, and can only be carried out in anaerobic environments
- formed directly from carbon dioxide and hydrogen
why is there limited out of water methane diffusion?
-bacteria in the aerobic zone will utilise it as it diffuses out (for carbon) so limited amounts are released from the water body
how to protezoa operate as predators in the anaerobic zone? (eg. hydrogenosomes)
-sulphur cilliates are the only predators
-adapted their mitochondria to form HYDROGENOSOMES which carry out anaerobic respiration
-contain symbiotic methanogenic bacteria (guild b)
-
how did hydrogenosomes form?
-from a past symbiotic relationship between cilliates and anaerobic bacteria
how do hydrogenosomes respire(reactants and products)?
-take pyruvate and convert it into acetate. this produces hydrogen and carbon dioxde in the process
how is methane produced from sulphur cilliates?
- methane producing bacteria that live on them utilised the produced hydrogen and carbon dioxide from the hydrogenosomes, converting it into methane
- alternatively, they break down the acetate into hydrogen and carbon dioxide, which are then used to produce methane
what are the primary producers in aerobic and anaerobic environments?
-aerobic: algae
Anaerobic: guild F
