Ch. 6 Microbial Nutrition and Growth
NADH
electron carrier
Cholesterol:
helps give structure to cell and form
Heme
in electron transport
Nitrogen requirements
> Anabolism often ceases because of insufficient nitrogen > Nitrogen acquired from organic and inorganic nutrients > All cells recycle nitrogen from amino acids and nucleotides > Nitrogen fixation by certain bacteria is essential to life on Earth
Organisms live in association with different species > Antagonistic relationships > Synergistic relationships > Symbiotic relationships
> Antagonistic relationships — a microbe harms another organism > Synergistic relationships — members of an association receive benefits that exceed those that would result if each lived by itself > Symbiotic relationships — organisms become interdependent and rarely live outside the relationship
Organisms classified into two groups based on source of carbon
> Autotrophs; use inorganic source of carbon; CO2 > Heterotrophs; catabolize organic molecules from other organisms
Organisms classified into two groups based on source of energy
> Chemotrophs; redox reactions from chemicals > Phototrophs; use light as energy source
Biofilms
> Complex relationships among numerous microorganisms > Form on surfaces, medical devices, mucous membranes of digestive system >> Form as a result of quorum sensing > Many microorganisms more harmful as part of a biofilm > Dental plaque is a biofilm that can lead to cavities > Scientists seeking ways to prevent biofilm formation
Complex media
> Exact chemical composition is unknown > Contain nutrients released by partial digestion of yeast, beef, soy, or proteins > Support growth of wide variety of microorganisms > Used to culture organisms with unknown nutritional needs
Microbial Growth Curve
> In the lag phase, the organisms are adjusting to their environment and do not reproduce immediately. NOT REPRODUCING > In the log phase, the population is increasing logarithmically, and the metabolic rate is at maximum. POP INCREASE, METABOLISM AT MAX > In the stationary phase, new organisms are produced at the same rate at which they are dying as nutrients are depleted and metabolic wastes accumulate. DIEING AT SOME RATE PRODUCED > In the death phase (or decline phase), the organisms are dying more quickly than they can be replaced by new organisms. ORGS DIE MORE QUICKLY AND REPLACED
Microbial Growth > Colony > Biofilm
> Increase in a population of microbes > Due to reproduction of individual microbes > Results in discrete colony or biofilm >> Colony — aggregation of cells arising from single parent cell >> Biofilm — collection of microbes living on a surface in a complex community
Inoculum introduced into nutrients called media
> Inocula obtained from various sources >> Environmental specimens >> Clinical specimens >> Stored specimens
Special Culture Techniques: Techniques developed for culturing microorganisms
> Low-oxygen culture >> Many organisms prefer intermediate oxygen levels >> Carbon dioxide incubators mimic the environment of many body tissues >>>Candle jars are a low cost alternative >>>> Ideal for the growth of capnophiles — microbes that grow best in high carbon dioxide levels
Culture Media
> Majority of prokaryotes have not been grown in culture medium > Nutrient broth is common medium > Agar is a common addition to many media >> Complex polysaccharide derived from certain red algae >> Produces a solid surface for colonial growth >> Most microbes cannot digest agar
Defined media
> Medium in which the exact chemical composition is known > Fastidious organisms require the addition of a large number of growth factors
Physical effects of water
> Microbes require water to dissolve enzymes and nutrients > Water is important reactant in many metabolic reactions > Most cells die in absence of water >> Some have cell walls that retain water >> Endospores and cysts cease most metabolic activity > Two physical effects of water >> Osmotic pressure >> Hydrostatic pressure
Measuring Microbial Reproduction: Direct methods not requiring incubation
> Microscopic counts >> Count microorganisms directly through a microscope >> Suitable for stained prokaryotes and large eukaryotes
Anaerobic media
> Obligate anaerobes must be cultured in the absence of free oxygen > Reducing media contain compounds that combine with free oxygen and remove it from the medium > Petri plates are incubated in anaerobic culture vessels >> Sealable containers that contain reducing chemicals
pH
> Organisms are sensitive to changes in acidity >> H+ and OH- interfere with H bonding > Neutrophiles grow best in a narrow range around neutral pH > Acidophiles grow best in acidic habitats >> Many microbes produce acidic waste products that can accumulate and inhibit their growth > Alkalinophiles live in alkaline soils and water
Growth Requirements
> Organisms use a variety of nutrients for their energy needs and to build organic molecules and cellular structures > Most common nutrients contain necessary elements such as carbon, oxygen, nitrogen, and hydrogen > Microbes obtain nutrients from variety of sources >> Sources of carbon, energy, and electrons
Organisms classified into two groups based on source of electrons
> Organotrophs — heterotrophs acquire electrons from same organic molecules that provide them carbon > Lithotrophs — autotrophs acquire electrons from inorganic molecules
Oxygen requirements: Aerobes Anaerobes Facultative anaerobes Aerotolerant anaerobes Microaerophiles
> Oxygen is essential for obligate aerobes > Oxygen is deadly for obligate anaerobes > How can this be true? >> Toxic forms of oxygen are highly reactive and excellent oxidizing agents ( oxidizes the microbe and itself and damages it.) >> Resulting oxidation causes irreparable damage to cells > Aerobes; require oxygen > Anaerobes; do not require oxygen > Facultative anaerobes; some aerobic organisms that can maintain life via fermentation and anaerobic respiration ( E.coli) > Aerotolerant anaerobes; tolerate oxygen by having enzymes to detox poisonous oxygen > Microaerophiles; require small amount of oxygen ( 2-10 %) Helicobacter pylori
Other chemical requirements
> Phosphorus > Sulfur > Trace element:Required only in small amounts > Growth factors:Necessary organic chemicals that cannot be synthesized by certain organisms
Osmotic pressure
> Pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membrane > Hypotonic solutions have lower solute concentrations >> Cell placed in hypotonic solution swells > Hypertonic solutions have greater solute concentrations >> Cell placed in hypertonic solution shrivels > Restricts organisms to certain environments >> Obligate and facultative halophiles
Obtaining Pure Cultures
> Pure cultures are composed of cells arising from a single progenitor >> Progenitor is termed a colony-forming unit (CFU) > Aseptic technique prevents contamination of sterile substances or objects > Two common isolation techniques >> Streak plates >> Pour plates
Other isolation techniques
> Some fungi are isolated with streak and pour plates > Protozoa and motile unicellular algae are isolated through dilution of broth cultures > Can individually pick single cell of some large microorganisms and use to establish a culture
Physical Requirements: Temp
> Temperature >> Temperature affects three-dimensional structure of proteins >> Lipid-containing membranes of cells and organelles are temperature sensitive >>>If too low, membranes become rigid and fragile >>> If too high, membranes become too fluid
Enrichment media
> Use of a selective medium to increase the numbers of a chosen microbe to observable levels > May require a series of cultures to enrich for the desired microbe > Cold enrichment used to enrich a culture with cold-tolerant species
Hydrostatic pressure
> Water exerts pressure in proportion to its depth > Barophiles live under extreme pressure >> Their membranes and enzymes depend on pressure to maintain their three-dimensional, functional shape
Culture
Act of cultivating microorganisms or the microorganisms that are cultivated
Biofilm example
Biofilms on teeth (dental plaque) can result in cardiovascular system infections like septicemia when bacteria from the biofilm enter the bloodstream from injuries to the oral cavity. Biofilms can also form on medical devices such as pacemakers and produce recurring infections. Respiratory equipment may also be colonized by biofilm-forming bacteria, contributing to respiratory infections. Some respiratory conditions, like cystic fibrosis, can create conditions which permit biofilm growth in the respiratory system, complicating existing respiratory problems.
Difference between colony and biofilm
Colony: growth from single cell Biofilm: community of dif micribes. Matrix, quorem chemical, grow on medical devices, teeth and GI Tract
Amino Acids:
Components of proteins
Six types of general culture media
Defined media Complex media Selective media Differential media Anaerobic media Transport media
Differential Media
Formulated so the presence of visible changes in the media or differences in the appearances of collies help to differentiate what is growing on the media. (Create visible changes on the plate, so you can differentiate what you're growing)
Preserving Cultures
Refrigeration Stores for short periods of time Deep-freezing Stores for years Lyophilization ( freeze dried) Stores for decades
Direct methods requiring incubation
Serial dilution and viable plate counts Membrane filtration Most probable number
Nutrients: Chemical and Energy Requirements
Sources of carbon, energy, and electrons
Generation Time
Time required for a bacterial cell to grow and divide Dependent on chemical and physical conditions
Why should cardiac nurses and respiratory therapists care about biofilms?
because they have suppressed Immune Systems and if you have biofilms they will get an infection! (ex. getting your teeth cleaned, a pt got cut and and got the biofilms in her cuts and became septic)