diversity.ppt

1、Section 2: Diversity of Microorganisms,Outline,The cause of physiological diversity: diverse habitats provide selective pressures over evolutionary time Biological and evolutionary insights from genomics Fundamentals of nutrition: carbon- and energy-source utilization provide a foundation for physio

2、logical ecology Selective pressures: ecosystem nutrient fluxes regulate the physiological status and composition of microbial communities Cellular responses to starvation: resting stages, environmental sensing circuits, gene regulation, dormancy, and slow growth,A planet of complex mixtures in chemi

3、cal disequilibrium A thermodynamic hierarchy describing biosphere selective pressures, energy sources, and biogeochemical reactions Using the thermodynamic hierarchy of half reactions to predict biogeochemical reactions in time and space Overview of metabolism and the “logic of electron transport” T

4、he flow of carbon and electrons in anaerobic food chains: syntrophy is the rule The diversity of lithotrophic reactions,1、THE CAUSE OF PHYSIOLOGICAL DIVERSITY: DIVERSE HABITATS PROVIDE SELECTIVE PRESSURES OVER EVOLUTIONARY TIME,2、BIOLOGICAL AND EVOLUTIONARY INSIGHTS FROM GENOMICS,Sequenced Genomes,2

5、007 Bacteria: 450 Archaea: 35 Eukaryotic: 15 2011 Bacteria: 17254 Archaea: 417 Eukaryotic: 2955,Genome size distribution ORF number Compared with human 3 billion bp 30000 ORF Habitat Genome size,The unknown category,Unknown No function Unexpressed in lab environment,General steps for an understandin

6、g of microbial function through genomic approach,Sequencing ORF Alignment Regulation networks 华丽的分割线 。 Biochemical assay Physiology assay Transcriptome assay Proteome assay Mutation (ii) slow growth; and/or (iii) dormancy.,Three Potential fates,Define of habitat by energy flux,Nutrient rich: 5 mg C/

7、 L / day Oligotroph: 0.1 mg C/ L / day Feast and famine constant,5、Cellular responses to starvation,Heat, Desiccation, Acidity, Irradiation, Salinity UV light,Environmentalsensing by bacteria.,All metabolic processes are reduced to a dormant or near-dormant state. When starved, many species will inc

8、rease in cell number resulting in reduced cell size. In the starvation/survival process, any cellular energy reserve material is used to prepare the cell for survival. All metabolic mechanisms are directed to the formation of specific proteins,ATP, and RNA so that the cell, when it encounters a subs

9、trate, is equipped to use it immediately without a The change to a smaller cell size on starvation (miniaturization) permits greater efficiency in scavenging what little energy-yielding substrates there are in the environment and also enhances survival prospects against other adverse environmental f

10、actors.,Starvation for a carbon (energy) source is different from starvation for a source of nitrogen, phosphorus, or sulfur,Many microorganisms accumulate intracellular storage bodies when nutrients are transiently abundant inthe cells immediate surroundings. Three main classes of cellular reserves

11、 are recognized: carbohydrates (polyglucans, glycogen), lipids (poly-hydroxy alkanoates, especially poly -hydroxybutyrate), and polyphosphates. Cyanophycin, a nitrogen source,Despite an innate genetic potential to grow with extreme rapidity in laboratory media, E. coli s doubling time in its native

12、habitat (the human intestine) is slowed about 35-fold. Immense range of doubling times.,As expected, energy demand during cellular maintenance is several orders of magnitude lower than for growth; while survival energy demand is orders of magnitude lower than that of maintenance. One shocking findin

13、g was that there seems to be no evidence of a minimum temperature for metabolism: even at a temperature of 40oC in ice, about one turnover of cellular carbon is expected every 108 years. Extremely slow rates of metabolism characteristic of dormancy work to counteract chemical instability of amino ac

14、ids (subject to racemization) and nucleic acids (subject to depurination). The extremely low energy requirements for DNA and protein repair during dormancy may be provided to microorganisms in deep, sometimes cold, habitats via slow diffusion of hydrogen gas from the adjacent geologic strata,6、 A planet of complex mixtures in chemical disequilibrium,Scientists understanding Microorganisms physiological sense,计算范例：,Eo & PE,3.7 A THERMODYNAMIC HIERARCHY DESCRIBINGBIOSPHERE SELECTIVE PRESSURES, ENERGY SOURCES, ANDBIOGEOCHEMICAL REACTIONS,3.8 USING THE THERMODYNAMIC HIERARCH