THEME 7

• Lineage: descent/ ancestry
• Phylum: a major lineage in one of the three domains of life
• Phylogeny: evolutionary history of and organism.
• Ecology: relationship of an organism with its environment
• Physiology: functions and processes allowing an organism to grow and multiply.
• Adaptation: processes allowing an organism to become better suited for living in its environment.
• Anaerobic respiration: a form of respiration in which the electron acceptor is not oxygen.

  Aerobic respiration: respiration that requires oxygen
• Oxygenic photosynthesis: photosynthesis in which oxygen is produced.
• Anoxygenic photosynthesis: photosynthesis which does not produce oxygen.
• Enrichment media: media that favour growth of certain bacteria.
• Metabolic diversity: defined in terms of cellular processes supporting growth (N fixing, iron oxidisers).
• Phylogenetic diversity: defined by evolutionary relationships btw organisms (defined by 16s ribosomal RNA phylogeny).
• Ecological diversity: defined in terms of microbial interactions btw organisms and their environment.
• Factors driving microbial diversity:

  1. Gene loss: a trait present in a common ancestor is lost during divergence.
  2. Convergent evolution: a trait has evolved independently in 2+ lineages and is not coded by homologous genes.
  3. Horizontal gene transfer: genes that code for a trait are homologous and have been exchanged btw distant related lineages.
• Phototrophic organism:

  • oxygenic and anoxygenic.
  • Able to conserve energy from light evolved early when earth was anoxic
  • Photosynthesis started w/ bacteria
  • 1st photo = anoxygenic (don’t generate O2, used H2 instead of H2O)
  • extensively diverse amongst anoxygenic
• Phototrophic organisms' common features:

  • chlorophyll like pigments to harvest energy to drive e- transfer and produce ATP
  • pigments found in intracellular membrane systems (better use of light in low intensities)
  • not all fix carbon
• 2 types of reaction centres: phototrophic

  1. FeS in photosystem I of oxygenic photosynthesis
  2. Q-type found in photosystem II of oxygenic photosynthesis
  3. Both found in cyanobacteria.
• Oxygenic phototrophic (Cyanobacteria).

  Genera: Prochlorococcus, Trichodesmium.
• Oxygenic phototrophic (Cyanobacteria):

  • 1st oxygen-evolving phototrophic
  • large, morphologically, ecologically heterogeneous group
  • 0.5-100 μm diameter
  • Morphological groups: unicellular/ filamentous
• Cyanobacteria General info:

  1. Chroococcales: unicellular, divide by binary fission (Includes prochlorophytes (unique, unicellular) )
  2. Pleurocapsales: unicellular, dividing by multiple fission (colonial)
  3. Oscillatoriales: filamentous nonheterocystous
  4. Nostocales: filamentous, divide on single axis, can differentiate
  5. Stigonematales: filamentous, divide in multiple planes, forming branching filament.
• Physiology & photosynthetic membranes of cyanobacteria

  • Oxy photos w/ FeS and Q-type photosystems
  • all fix CO2 by Calvin cycle
  • many fix N2 - most synthesise own vitamins
  • harvest energy from light and fix CO2 during day
  • generate energy by fermentation/ aerobic respiration of stored C products
  • Thylakoids: specialised membrane systems that increase ability to harvest light energy, typically arranged in concentric circles around cytoplasm periphery
  • produce pigments (chlorophyll a and phycobilin’s)
• Physiology

  • germination and vegetative growth Some form akinetes (resting structure w/ thickened outer walls to protect from darkness, desiccation, or cold).
• Physiology and motility:

  • motility mechanisms but NO flagella
  • Gliding motility when in contact w/ solid surface, another cell/ filament
  • some form hormogonia (short, motile fragments, break off to disperse under stress)
  • show phototaxis, sometimes chemo - gas vesicles (regulate buoyancy), for positioning in water column where low light intensity