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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 micro- nutrients
Major Nutritional Types: (see Table 5.2)
Energy → Electrons → Carbon
• Photolithoautotrophy
• Photoorganoheterotrophy
• Chemolithoautotrophy
• Chemoorganoheterotrophy
• 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:Passive Diffusion
Facilitated Diffusion
Transport Types:Primary Active Transport
ATP-Binding Cassette Transporter (ABC transporter)
• Against concentration gradient requires energy.
• “Primary” transporters directly use ATP for energy.
• May require solute binding proteins to scavenge solute.
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.
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