Mountain gorillas in Uguanda munch on rotting wood, which makes up only 4% of their diet, but provides 95% of their sodium requirements. Lecture 7B outline: Nutrition: Make it or take it continued Previous lecture described autotrophs (both photoautotrophs & chemoauthotrophs) This lecture: Heterotrophs - Can?t make food so they take it Photoheterotroph - rare among prokaryotes Ex. Purple sulfur bacteria Chemoheterotroph - majority of prokaryotes Saprobes & parasites Tremendous diversity in organic molecules that can serve as food Ex. E. coli, Lactobacillus, common invaders of sewage treatment Bacteria living as biofilms Course Objectives 4. Living things are highly ordered and need to make a living by acquiring and transforming energy 6. Living things develop in an orderly and controlled manner and are influenced by genetic and environmental factors 9. Science is a way of understanding and producing explanations of nature One of Many Alternate Phylogenetic Hypotheses of Tree of Life Freeman Fig. 1.8 Bacteria Archea Eukarya - or Eukaryotes Universal ancestor (prokaryote) Brock 4.1 Simplified view of cell metabolism in prokaryote Today?s lecture: Obtaining Nutrition (Carbon and other chemicals) for Biosynthesis Autotrophs Heterotrophs ATP ATP Carbon & nutrients The big picture: Procuring energy for metabolism & Procuring nutrients from ?food? Krebs or Heterotrophs must solve the same Problems as Autotrophs During Nutrient Uptake and Digestion How to collect raw materials and energy required for growth and development. How to process complex substrates into a simpler form that can be utilized by the organism. Note that problems of obtaining carbon for biosynthesis are much the same as those for obtaining energy for respiration & metabolism There Are Only Two Ways For Organisms to Obtain Resources, Metabolites, and Energy Make them from scratch: autotrophism. Autotrophs convert inorganic elements into organic molecules (fixation), and capture chemical energy from non-living sources. Steal them from others: heterotrophism. Heterotrophs must extract chemical energy and needed organic molecules (sugars, etc.) from either autotrophs or other heterotrophs. Autotrophs and Heterotrophs Have Different Macronutrient Requirements Macronutrients: materials needed in large quantities. Usually major structural components, substrates,etc. Autotrophs: water, inorganic carbon source (usually CO2 or CH4), nitrogen. Lesser quantities needed of Na, K, P, S, Mg. Heterotrophs: water, fixed carbon (glucose is most common), fixed nitrogen (amino acids). Free minerals req'd include Na, K, P, Ca. Fixed refers to conversion to form that heterotroph can use Autotrophs and Heterotrophs Have Different Micronutrient Requirements Micronutrients: materials needed in small quantities. Co-factors for enzymes, ions used in reaction centers, etc. Autotrophs, heterotrophs both: trace elements and metals (Fe, Cu, B, Mo, Ni, Si, Mn, etc.). Heterotrophs: organic vitamins and co-factors such as Vit. B-series, biotin, folic acid. NOTE: precise macro- & micronutrient requirements often differ among species. Autotrophs synthesize glucose Autotrophs metabolize glucose, too Heterotrophs metabolize glucose but often don?t eat pure glucose Recall energy sources covered in previous lecture Campbell Table 27.1 Groups of Organisms Based on Energy Source & Carbon Source Photoheterotrophs - rare among heterotrophs Light is the energy source Organic compound is the carbon source These pathways are regarded as novel ones and confer competitive success in nature Ex: purple nonsulfur bacteria ?eat? an organic carbon source, such as that found in mud, lake water or sewage They live in environments high in H2S & CO2or H2 and CO2 Brock 13.7 Purple nonsulfur bacteria - photoheterotrophs Use light for energy source and organic compound as carbon source (e.g. fatty acids, amino acids, alcohols, aromatic compounds); most can fix N2) Brock 13.91 Photoheterotroph: green sulfur bacterium Chlorosomes - contain bacteriochlorophyll Does not undergo ?typical? photosynthetic rxns -majority of prokaryotes Saprobes - decomposers that absorb nutrients from dead organic matter Parasites - absorb nutrients form body fluids of living hosts Chemoheterotrophs - Organic compound is both the carbon source & energy source, but specific carbon source varies Ex. E. coli - requires only glucose for organic nutrient Ex. Lactobacillus - grows well only under all 20 a.a., several vitamins, & other organic compounds Freeman Chapter 14 E. coli in human intestine - an environment where types & amounts of available nutrients are constantly changing. Fig. 27-15 1 µm Campbell & Reece Fig 27.15 A biofilm consisting of numerous bacterial species that forms on tooth surfaces ? an example of metabolic cooperation between species Bacteria settle onto surface. Cells lose motility and attach, using a polysaccharide slime 4. Growing colonies join to form a biofilm 5. Biofilm matures and releases single cells Image from: http://www2.binghamton.edu/biology/faculty/davies/research.htm (Washington Post, March 9, 2009) Image from: http://www.coral.org/node/4117 The brown tube sponge Agelas conifera generates a compound that breaks up biofilms. (Washington Post, March 9, 2009) Raven et al. 14-4 Bacterium Pseudomonas marginalis, widespread in soils So, Who Are the Heterotrophs? Most bacteria (except photosynthetic forms) Fungi Non-photosynthetic protists Unicellular and multicellular animals In short, any organism that must consume another, and cannot synthesize raw materials from strictly inorganic sources.
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