Factors affecting Microbial Growth

Factors Affecting Microbial Growth and Survival

• Nutrient content and antimicrobial content significantly impact microbial growth and survival.

Effect of Nutrient Content

• Nutrients are essential for biosynthesis and energy release, fulfilling microbial growth requirements.
• Complex carbohydrates, simple sugars, nitrogen, fats, vitamins, and minerals are necessary nutrients.

Nutrient Sources and Microorganisms

• Carbohydrates from cereals and fruits support Aspergillus restrictus, Eurotium glaucus, and Penicillium.
• Proteins from cereals, meat, fish, eggs, and milk aid Staphylococcus aureus, Salmonella, Campylobacter jejuni, and Listeria monocytogenes.
• Vegetable oils, meat, fish, and beans provide lipids for Pseudomonas spp.
• Minerals are obtained from vegetables, fruits, and seafood, benefiting Plesiomonas shigelloides.
• Vitamins from milk, meat, vegetables, and cereal support Bacillus megaterium and Streptomyces olivaceus.

Macronutrients/Macro-elements

• Carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus are key components of carbohydrates, lipids, and proteins.
• Potassium (K+) is important for enzyme-protein synthesis and membrane function.
• Calcium (Ca2+) increases heat resistance in bacterial endospores and strengthens cell walls.
• Magnesium (Mg2+) acts as a cofactor, stabilizing cell membranes and ribosomes.
• Iron (Fe2+ and Fe3+) is part of cytochrome and cofactors for enzymes, aiding in excretion of proteins located in the cell fluid.

Carbon, Hydrogen, and Oxygen

• Important elements found in organic molecules.

Phosphorus

• Phosphorus is present in nucleic acids, phospholipids, nucleotides (like ATP), as well as cofactors, various protein types and other cell components.
• Microbes can directly incorporate inorganic phosphate to fulfill their phosphorus needs.
• Microbial growth in aquatic environments is often limited by low phosphate levels.

Nitrogen

• Nitrogen is used for synthesizing amino acids, purines, pyrimidines, and certain enzyme cofactors.
• Some organisms assimilate ammonia directly via enzymes such as glutamate dehydrogenase, glutamine synthetase, and glutamine synthase.
• Nitrogen fixation converts atmospheric nitrogen into usable forms.

Sulfur

• Microorganisms utilize sulfate as a source of sulfur.
• It is reduced through assimilatory sulfate reduction.
• Cysteine, a reduced form of sulfur, is also utilized.

Electrons

• Electrons are part of the electron transport chain which relates to for oxidation-reduction reactions: energy for use in cellular work.
• Molecules are reduced during biosynthesis, converting CO2 into organic molecules.

Micronutrients/Trace Elements

• These nutrients are required in small amounts.
• They are parts of enzymes and cofactors.
• They aid in catalysis, reaction and maintenance of protein structure.
• Manganese (Mn2+) is for phosphate group transfer.
• Molybdenum (Mo2+) aids Nitrogen fixation
• Cobalt (Co2+) forms Vitamin B12

Nutritional Classification

• Organisms are classified based on their energy, electron, and carbon sources.
• Energy sources power metabolic pathways.
• Electron sources supply electrons to the electron transport chain.
• Carbon sources provide carbon for cell component creation.

Microbial Transport

• The plasma membrane regulates molecule entry and exit to maintain internal environment.
• Nutrients from the external environment are transported across the cell membrane via selective proteins in the phospholipid bilayer.

Nutrient Uptake

• Spontaneous movement of solute particles across concentration, electric, or pressure gradients.
• Particles move from high to low concentration until equilibrium is achieved.
• Permeability relies on lipid solubility and molecular size.

Facilitated Diffusion

• It employs a concentration gradient
• Requires specialized integral membrane proteins to help solutes
• Said proteins are a type of carrier protein
• The membrane is part is the location
• Channels or pores across barrier is provided
• Specificity is seen here
• Only particular molecules are allowed to pass
• Structurally similar solutes go pass competitive inhibition
• Equilibrium is reached faster than passive diffusion here
• A Reversible process

Glucose Transporters

• This is a big group of proteins on membrane
• Transports glucose across the cell membrane
• Has two conformational states
• Substrate binders located outward
• The spot for binding is inward

Aquaporins (AQP)

• Water transfer channels
• Sometimes these proteins transfer small solutes across the membrane
• Can be found on cell membranes of different bacteria, fungi, animals and plants
• Water flows faster in organisms with aquaporins compared to organisms that diffused in the phospholipid bilayer

Ion Channels

• Proteins pass through cell membrane
• Ions pass through one side of the membrane to the other.
• H2O solvent that becomes ions can get in after the structural changes
• Changes that allows the channel to open

Ligand-Gated Ion Channels

• Ion channels specific transmembrane proteins.
• Opens to let ions flow through membrane
• Does that with sodium, potassion, calium or cloride
• Done as one responds to messenger, such as neurotransmitter

G protein–coupled receptor (GPCR)

• Receptor wity seven-transmembrane, heptahelical proteins
• In cell membrane
• Binds extracellular material
• Signals transmit to intracellular molecule: G guanine protein

Voltage–Gated Ion Channels

• Group of integral membrane proteins
• Form ion channels
• Changes in the membrane's electrical potential activate the channels.
• Opening and closing regulated

Ionophores

• Lipid-soluble entities
• Transports ions through cell membrane
• Compunds speed that ion transport through cell membranes

Examples of Ionophores

• Gramicidin A: Moves H, Na, K
• 2,4-Dinitrophenol (DNP): Moves H
• Ionomycin : Moves Ca2
• Lasalocid: Moves K, Na, Ca2, Mg2
• Monensin :Moves Na, H

Active Transport

• The use of the metabolic energy for transport through carrier proteins
• Carrier proteins are in the membrane
• Drives particles through membrane
• Needs energy

Active Transport Types

• Active Primary- Has chem energy for transport- example: ATP
• ATP binding casette system example
• Substrate binding ptotein- binds to substrate
• Protein spanning proteins, a carrier type
• Area to bind ATP, where hydrolysis happens and energy is released

Sodium–Potassium Pump

• Found in cell membranes
• Powered by ATP
• Moves sodium and Potassion in opposite direction
• Works against concentrations
• 3 Na out and 2 K in, single run

Secondary active transport

• Energy from proton charge used.

Positive Ions Accumulate

• Postively charged ones load on the negatively charged cell.

Group Translocation

• Active transport, energy-rich.
• Energy doesnt come from ATP.
• Altered and carries the stuff.
• Mechanism allows to bind
• Happens on cell sruface
• Structure changes and passages the membrance

Iron Uptake

• Little amount of the material available
• Limits the amount of growth
• Microbes bind with sidrophores to make the iron.

Culture Media

• Prepped in soild/liquid form to help store, grow and transport microorganisms.
• Complex with liguid in the medium from urine or meat broth- Luis Paster
• Solid: potato and gel, robert kock
• Gel melts at 24
• It serves as a good susbtrate

Agar

• Hesse first wrote about it
• Agar plate with 1-2% mostly 1.5% present
• polymer sulphated from galactosse
• Red Algae material
• 90 C melts it
• 45 c solid
• Microbrs on a wide-temperature agar medium
• Hardening good, cant be degraded by the bacteria

Silica gel

• Used to develop authrophic bactetia

Chemical Properties-Media

• Only ingridents super pure
• Doesnt have anything fromt issue- Yest, Plants

Compositions-chemical

• Complex medium can feed all differnt kinds of microorganisms
• Contain some parts chemicaly unclear

Supportive media

• Genera purpose type
• Sustain growth of microorganisms
• Triptic soy broth/agar

Culture media - Functional Type: Enriched Media

• Include blood, etc
• For quick microorganisms
• Foritied media
• Blood agar

Selective Media

• Specific microrganisms grow
• Test the material's reactions.

Differential Media

• Help tell kinds of different kinds of microbes
• Show characteristics
• Blood agar and bacterial actions

AntiMicroibal Substances

• Impede micro growth in food
• The foods have ingridents that prevent
• In from foods
• micoorganism make it
• Foods made from it.

Natural Antimicrbials

• Are in some foods that keep from decay

Food/AntiMirobials

• Cloves- eugenol
• cinnamic aidehyld- cinnamon, sage
• Thymol/lsothymol- sage , oregano
• Allcin- Garllic
• Isothiocyante- allyl- Mustered
• Immu, coglu,lacto- Milk
• Egges Lacto- Lysoyme

Antimicrobials

• Made by microorganisms

Organisms/micro-organisms

• Propionic bacteria/Propioic Acid/ Molds
• Lactic bact/H2o2/ S. aureus. b cerus * Yeast/alcohol Alcohol
• Lactous lacti-/lactate -l monocytogenis
• L reuteri/ l reuteri= e coli h77/l monocytogens

Added substances to food

• Preservatives
• Nutrition
• Favoring agents
• Colorings
• Texturing agents
• Various

Types compounds:

• Suger, salt, smoking, spices, vinegars, alcohol

Other additives

• Organix acids- Acetate, acetetic
• Nonorganic- carbonic, sulfuoric acids
• Agents

Packaing:

• Has materials to prevent decay