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)