Nutritional Strategies and Nutrient Acquisition

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Transcript Nutritional Strategies and Nutrient Acquisition

Nutritional Strategies and
Nutrient Acquisition
• Nutritional Strategies (Types)
– Required Resources
– Nutritional Types
• Nutrition Acquisition
– Passive transport
– Active transport
– “Scavenging”
Resources for All Life:
• Energy: cells need to do the work of membrane transport,
biosynthesis, and mechanical processes.
• Electrons: anabolic reactions (biosynthesis) require reducing
power (adding e-).
• Major Elements (macronutrients): Carbon, Nitrogen,
Phosphorous in varying proportions (e.g. C:N:P ratio of
eukaryote algae ≈ 106:16:1; bacteria ≈ 100:25:1; fungi ≈
400:20:1). These, along with O, H and S, are all supplied in
organic or inorganic form. In lesser amounts are Fe, Mg, Ca,
K, and Na, which are mostly supplied as inorganic forms.
• Trace Elements (micronutrients): Mn, Zn, Co, Cu, Mo, & Ni.
• Growth Factors: essential amino acids, vitamins, and
nucleoside bases are needed for growth but cannot be made
by many organisms; some are sources of macro- and micronutrients
Major Nutritional Types: (see Table 5.2)
Energy → Electrons → Carbon
• Photolithoautotrophy
• Photoorganoheterotrophy
• Chemolithoautotrophy
• Chemoorganoheterotrophy
Transport Types:
Passive Diffusion
Facilitated Diffusion
• Both follow a concentration gradient,
high to low; therefore reversible.
• Passively through membrane lipids
or porins; rate increase linear.
• Facilitated by selective transporters;
rate increase with [S] then plateaus at
“saturation”.
Transport Types:
Primary Active Transport
• Against concentration
gradient requires energy.
• “Primary” transporters
directly use ATP for energy.
• May require solute binding
proteins to scavenge solute.
ATP-Binding Cassette Transporter
(ABC transporter)
Transport
Types:
Secondary Active
Transport
• Solute transport against
a concentration gradient.
• Secondary transporter
couples solute with a flow
of protons or other ions
along strong concentration
gradients; energy source.
• Mechanism may be
antiport or symport.
Transport Types:
Group Translocation
• Solute can transport against
concentration gradient.
• Solute is modified during
transport and energy released.
• Often a high energy P-group
gets translocated in a cascading
sequence toward a lower energy
state.
• e.g. phosphoenolpyruvate
(PEP): sugar phosphotransferase
system (PTS).
• PST is involved in chemotaxis.
“Send out the
scavengers!”
Siderophores
• Iron bioavailability is
low; “rust never sleeps”.
• Bacteria release these
scavenger molecules to
facilitate iron transport.
• Multiple siderophores
complex an iron
molecule.
• Siderophores can be
species specific.