-
Nutrition
Chemical substances are acquired from the environment and usedin cellular activities
-
Essential nutrients
Must be provided to an organism
-
Macronutrients
- • Required in large quantities
- • Play principal roles in cell structure and metabolism
- • Proteins, carbohydrates
-
Micronutrients or trace elements
- • Required in small amounts
- • Involved in enzyme function and maintenance of protein structure
- • Manganese, zinc, nickel2
-
Organic nutrients
- Contain carbon and hydrogen atoms and are usually theproducts of living things
- Methane (CH4), carbohydrates, lipids, proteins, and nucleicacids
-
Inorganic nutrients
- Atom or molecule that contains a combination of atoms other than carbon and hydrogen
- Metals and their salts (magnesium sulfate, ferric nitrate,sodium phosphate), gases (oxygen, carbon dioxide) andwater
-
Chemical Analysis of Microbial Cytoplasm
- – 70% water
- – Proteins
- – 96% of cell is composed of 6 elements
- :• Carbon
- • Hydrogen
- • Oxygen
- • Phosphorous
- • Sulfur
- • Nitrogen
-
• Sources of Essential Nutrients
- – Carbon
- – Nitrogen
- – Oxygen
- – Hydrogen
- – Phosphorous (Phosphate Sources)
- – Sulfur
-
Heterotroph
- • Must obtain carbon in an organic form made by otherliving organisms
- • Such as proteins, carbohydrates, lipids, and nucleicacids
-
Autotroph
- • An organism that uses CO2 as its carbon source
- • Not nutritionally dependent on other living things
-
Nitrogen Sources
- – Main reservoir is nitrogen gas (N2)
- • 79% of earth’s atmosphere is N2– Nitrogen is part of the structure of proteins, DNA, RNA andATP
- • These are the primary source of N for heterotrophs– Some bacteria and algae use inorganic N sources
- • NO3-, NO2-, or NH3– Some bacteria can fix N2.– Regardless of how N enters the cell, it must be converted toNH3
- • The only form that can be combined with carbon to synthesize aminoacids, etc.
-
Oxygen Sources
- – Major component of carbohydrates, lipids, nucleicacids, and proteins
- – Plays an important role in structural and enzymaticfunctions of cell
- – Component of inorganic salts (sulfates,phosphates, nitrates) and water
- – O2 makes up 20% of atmosphere
- – Essential to metabolism of many organisms
-
Hydrogen Sources
- – Major element in all organic compounds andseveral inorganic ones (water, salts, and gases)
- – Gases are produced and used by microbes
- – Roles of hydrogen:
- • Maintaining pH
- • Acceptor of oxygen during cell respiration
-
Phosphorous (Phosphate Sources)
- – Main inorganic source is phosphate (PO4-3)
- • Derived from phosphoric acid (H3PO4) found in rocks andoceanic mineral deposits
- – Key component of nucleic acids, essential togenetics
- – Serves in energy transfers (ATP)
-
Sulfur Sources
- – Widely distributed in environment, rocks;sediments contain sulfate, sulfides, hydrogensulfide gas and sulfur
- – Essential component of some vitamins and the amino acids: methionine and cysteine
- – Contributes to stability of proteins by forming disulfide bonds
-
Other Nutrients Important in MicrobialMetabolism
- – Potassium – essential to protein synthesis and membrane function
- – Sodium – important to some types of cell transport
- – Calcium – cell wall and endospore stabilizer
- – Magnesium – component of chlorophyll; membraneand ribosome stabilizer
- – Iron – component of proteins of cell respiration
- – Zinc, copper, nickel, manganese, etc.
-
Growth Factors: Essential Organic Nutrients
- • Organic compounds that cannot be synthesized by an organism because they lack the genetic and metabolic mechanisms to synthesize them
- • Growth factors must be provided as a nutrient– Essential amino acids, vitamins
-
Main determinants of nutritional type are
- – Carbon source – heterotroph, autotroph
- – Energy source
- • Chemotroph – gain energy from chemical compounds
- • Phototrophs – gain energy through photosynthesis
-
• Autotrophs and Their Energy Sources
- – Photoautotrophs
- • Oxygenic photosynthesis
- • Anoxygenic photosynthesis
- – Chemoautotrophs
- • lithoautotrophs
- • survive totally on inorganic substances
- – Methanogens
- • A kind of chemoautotroph
- • Produce methane gas under anaerobic conditions
-
• Heterotrophs and Their Energy Sources
- – Majority are chemoheterotrophs
- • Aerobic respiration– Two categories
- • Saprobes– Free-living microorganisms that feed on organic detritusfrom dead organisms
- – Opportunistic pathogen
- – Facultative parasite
- • Parasite– Derive nutrients from host
- – Pathogens
- – Some are obligate parasites
-
• Passive transport
- – does not require energy; substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration
- – Diffusion
- – Osmosis – diffusion of water
- – Facilitated diffusion – requires a carrier
-
• Active transport
- – requires energy and carrier proteins;gradient independent
- – Active transport
- – Group translocation – transported molecule chemically altered
- – Bulk transport – endocytosis, exocytosis, pinocytosis
-
• Niche
– Totality of adaptations organisms make to theirhabitat
-
• Environmental factors affect the function of metabolic enzymes
• Factors include
- – Temperature
- – Oxygen requirements
- – pH
- – Osmotic pressure
- – Barometric pressure
-
• Three Cardinal Temperatures
- – Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism
- – Maximum temperature – highest temperaturethat permits a microbe’s growth and metabolism
- – Optimum temperature – promotes the fastest rate of growth and metabolism
-
• Three Temperature Adaptation Groups
- – Psychrophiles – optimum temperature below15oC; capable of growth at 0oC
- – Mesophiles – optimum temperature 20o-40oC;most human pathogens
- – Thermophiles – optimum temperature greater than 45oC
-
• Gas Requirements
- – Oxygen– As oxygen is utilized it is transformed into several toxic products:
- • Singlet oxygen (1O2), superoxide ion (O2-), peroxide (H2O2), and hydroxyl radicals (OH-)
- – Most cells have developed enzymes that neutralize these chemicals:
- • Superoxide dismutase, catalase– If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats
-
1 Aerobe
2 Obligate aerobe
3 Facultative anaerobe
4 Microaerophilic
5 Anaerobe
6 Obligate anaerobe
7 Aerotolerant anaerobes
- 1 utilizes oxygen and can detoxify it
- 2 cannot grow without oxygen
- 3 utilizes oxygen but can also growin its absence
- 4 utilizes oxygen but can also growin its absence
- 5 does not utilize oxygen
- 6 lacks the enzymes to detoxify oxygenso cannot survive in an oxygen environment
- 7 do not utilize oxygen but can survive and grow in its presence
-
• Carbon Dioxide Requirement
- – All microbes require some carbon dioxide in their metabolism
- – Capnophile – grows best at higher CO2 tensions than normally present in the atmosphere
-
• Effects of pH
1 Obligate acidophiles
2 Alkalinophiles
- Majority of microorganisms grow at a pH between6 and 8
- 1 grow at extreme acid pH
- 2 grow at extreme alkaline pH
-
• Osmotic Pressure
1 Halophiles
2 Osmotolerant
- Most microbes exist under hypotonic or isotonic conditions
- 1 require a high concentration of salt
- 2 do not require high concentration of solute but can tolerate it when it occurs
-
Other Environmental Factors
• Barophiles
can survive under extreme pressure and will rupture if exposed to normal atmospheric pressure
-
• Symbiotic
1 Mutualism
2 Commensalism
3 Parasitism
- two organisms live together in aclose partnership
- 1 obligatory, dependent; both members benefit
- 2 commensal member benefits,other member neither harmed nor benefited
- 3 parasite is dependent and benefits;host is harmed
-
Non-symbiotic
1 Synergism
2 Antagonism
- organisms are free-living;relationships not required for survival
- 1 members cooperate to produce aresult that none of them could do alone
- 2 actions of one organism affect the success or survival of others in the same community (competition)
- • Antibiosis
-
• Interrelationships Between Microbes andHumans
- Human body is a rich habitat for symbiotic bacteria, fungi, and a few protozoa
- normal microbial flora
- Commensal, parasitic, and synergistic relationships
-
• Biofilms
- result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers
- • Dominate the structure of most natural environments on earth
- • Communicate and cooperate in the formation and function of biofilms – quorum sensing
-
• Microbial growth occurs at two levels
• Division of bacterial cells occurs mainly throughbinary fission (transverse)
- – Growth at a cellular level with increase in size
- – Increase in population
- – Parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells
-
• Rate of Population Growth
- – Time required for a complete fission cycle is called the generation, or doubling time
- – Each new fission cycle increases the population by a factor of 2
- – exponential growth– Generation times vary from minutes to days
-
• The Population Growth Curve
1 Lag phase
2 Exponential growth phase
3 Stationary phase
4 Death phase
- 1 “flat” period of adjustment, enlargement; little growth
- 2 a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment
- 3 rate of cell growth equals rate of celldeath caused by depleted nutrients and O2, excretion oforganic acids and pollutants
- 4 as limiting factors intensify, cells die exponentially
-
Methods of Analyzing Population Growth
- • Turbidometry – most simple
- • Degree of cloudiness, turbidity, reflects the relative population size
- • Enumeration of bacteria:
- – Viable colony count
- – Direct cell count
- – count all cells present;automated or manual
-
Metabolism
1 Catabolism
2 Anabolism
- all chemical and physical workings of a cell
- 1 degradative; breaks the bonds of larger molecules forming smaller molecules; releases energy
- 2 biosynthesis; process that forms larger macromolecules from smaller molecules; requires energy input
-
Enzymes
- are biological catalysts
- –Lower the energy of activation
- – The energy of actvation is the resistance to a reaction
- – The enzyme is not permanently altered in the reaction
- • Enzymes use a specific lock and key fit with substrate
-
1 Simple enzymes
2 Holoenzymes
- 1 consist of protein alone
- 2 contain protein and nonprotein molecules
- Apoenzyme-protein portion
- Cofactors–nonprotein portion
- • Metallic cofactors: iron,copper,magnesium
- Coenzymes,organicmolecules:vitamins
-
• Enzyme Specificity and the Active Site
1 active site,orcatalytic site
2 induced fit
- Appropriate reaction occurs;product is formed and released
- 1 Site for substrate binding
- 2 A temporary enzyme-‐substrate union occurs when substrate moves into active site
-
- 1. Transported extracellularly
- They break down large food molecules or harmful chemicals
- Cellulase, amylase, penicillinase
- 2. retained intracellularly and function there
- Most enzymes are endoenzymes
-
1. Constitutive enzymes
2. Regulated enzymes
-
1. Always present
- Always produced in equal amounts or at equal rates
- Enzymes involved in glucose metabolism
- 2.Not constantly present
- Production is turned on (induced) or turned off (repressed) in response to changes in concentration of the substrate
-
Synthesis or condensation reactions
-
– Anabolic reactions to form covalent bonds
- – Between smaller substrate molecules
- – Require ATP
- – Release one molecule of water for each bond formed
-
-
– Catabolic reactions that break down substrates into small molecules
– Requires the input of water to break bonds
-
Sensitivity of Enzymes to Their Environment
-
Activity of an enzyme is influenced by cell’s environment
- • Temperature
- – Reduce activity
- – Denature
- • pH
- – Reduce activity
- – Denature
- • Substrate concentration
- – Reaches a saturation point
-
Direct Controls on the Actions of Enzymes
1. Competitive inhibition
2. Noncompetitive inhibition
3. Enzyme repression
4. Enzyme induction
- 1. Competition for the active site
- 2. Allosteric enzymes
- The binding by a substance to a site other than the active site
- 3.Inhibits at the genetic level by controlling synthesis of key enzymes
- 4. Enzymes are made only when suitable substrates are present
-
1.Energy
2.Forms of energy
-
1. The capacity to do work or to cause change
2. Thermal, radiant, electrical, mechanical, atomic, and chemical
-
Cell Energetics
1. Endergonic reactions
2. Exergonic reactions
-
Cells manage energy in the form of chemical reactions that make or break bonds and transfer electrons
- 1. consume energy
- 2. release energy
-
Redox reactions
- Always occur in pairs
- There is an electron donor and electron acceptor which constitute a redox pair
- Process salvages electrons and their energy
- Released energy can be captured to phosphorylate ADP or another compound
-
Electron and Proton Carriers
- Repeatedly accept and release electrons and hydrogen to facilitate the transfer of redox energy
- – Most carriers are coenzymes:
- • NAD+
- • FAD
- • NADP
- • coenzyme A
- • Compounds of the respiratory chain
-
Adenosine Triphosphate: ATP
- – Metabolic “currency”
- – Three part molecule consisting of
- • Adenine
- – a nitrogenous base
- • Ribose
- – a 5--‐carbon sugar
- • 3 phosphate groups
- – ATP utilization and replenishment is a constant cycle in active cells
- – Removal of the terminal phosphate releases energy
-
ATP can be formed by three different mechanisms
- 1. Substrate -level phosphorylation
- – transfer of phosphate group from a phosphorylated compound (substrate) directly to ADP
- 2. Oxidative phosphorylation – series of redox reactions occurring during respiratory pathway
- 3. Photophosphorylation – ATP is formed utilizing the energy of sunlight
-
Primary catabolism of fuels (glucose) proceeds through a series of three coupled pathways
-
1. Glycolysis
- 2. Kreb’s cycle
- 3. Respiratory chain, electron transport
-
Nutrient processing is varied, yet in many cases is based on three catabolic pathways that convert glucose to CO2 and gives off energy
- 1.Aerobic respiration
- – glycolysis, the Kreb’s cycle, respiratory chain
- 2.Anaerobic respiration
- – glycolysis, the TCA cycle, respiratory chain; molecular oxygen is not final electron acceptor
- 3.Fermentation
- – glycolysis, organic compounds are the final electron acceptors
-
-
– Series
- or
- enzyme--‐catalyzed
- reac+ons
- in
- which
- electrons
- are
- transferred
- from
- fuel
- molecules
- (glucose)
- to
- oxygen
- as
- a
- final
- electron
- acceptor
- Glycolysis – glucose (6C) is oxidized and split into 2 molecules of pyruvic acid (3C), NADH is generated
- TCA – processes pyruvic acid and generates 3 CO2 molecules , three NADH and one FADH2are generated
- Electron transport chain – accepts electrons from NADH and FADH; generates energy through sequential redox reactions called oxidative phosphorylation
-
ATP Totals
1.Glycolysis
2.Pyruvate to Acetyl CoA
3.Kreb’s cycle
4.Total
- 1. 2 NADH = 6 ATP
- Plus 2 ATP
- 2. 2 NADH=6 ATP
- 3. 6 NADH= 18 ATP
- 2 FADH2 = 4 ATP
- Plus 2 ATP
- 4. 38 ATP
-
Anaerobic Respiration
- Functions like aerobic respiration
- • Except it utilizes other electron acceptors rather than oxygen
- • Nitrate (NO3 --‐) and nitrite (NO2 --‐)
- • Used by anaerobes and facultative anaerobes
|
|
