Microbial Nutrition Quiz

Microbial Nutrition

• Nutrients: substances acquired from the environment and used for cellular activities
• Essential nutrients: substances necessary for growth and cannot be synthesized by the organism
• Macronutrients: required in large amounts for cell structure and metabolism; examples include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur
• Micronutrients (trace elements): required in small amounts for enzyme function and protein structure
• Organic nutrients: contain carbon and hydrogen, usually produced by living things; examples include carbohydrates, fats, proteins, and vitamins
• Inorganic nutrients: simple molecules containing elements other than carbon and hydrogen; examples include water, salts, and gases

Carbon Sources

• Heterotroph: obtains carbon from organic sources, dependent on other living organisms
• Autotroph: uses inorganic CO₂ as its carbon source, capable of converting CO₂ into carbon compounds, not dependent on other living things

Nitrogen Sources

• NH₃ (ammonia) is the primary nitrogen source for heterotrophs
• Nitrogen must be converted to NH₃ before entering the cell
• NH₃ is the only form that can be directly combined with carbon to synthesize amino acids and other compounds

Oxygen Sources

• Oxygen plays a vital role in cell structure and enzymatic functions
• It is a major component of carbohydrates, lipids, nucleic acids, and proteins
• Oxygen acts as a final electron acceptor in aerobic respiration, generating ATP

Hydrogen Sources

• Hydrogen is essential for maintaining pH, forming hydrogen bonds, and serving as an energy source in redox reactions

Phosphorous (Phosphate) Sources

• The main inorganic source is phosphate (PO₄)
• It's a key component of nucleic acids and is essential for cellular genetics

Sulfur Sources

• Sulfur is found in rocks and sediments
• It's a component of vitamins and amino acids like methionine and cysteine
• Sulfur forms disulfide bridges that contribute to protein shape and structural stability

Essential Organic Nutrients

• Growth factor: an organic compound that an organism cannot synthesize and must be obtained from its environment; examples include amino acids, nitrogenous bases, and vitamins

How Microbes Feed: Nutritional Types

• Phototroph: obtains energy from light rays for cell metabolism, they are autotrophs
• Chemotroph: obtains energy from chemical compounds, they are heterotrophs

Autotrophs and Their Energy Sources

• Photoautotrophs: capture light energy and convert it into chemical energy for metabolism, produce organic molecules used by themselves and heterotrophs
• Chemoautotrophs: obtain energy from inorganic substances, they are classified into chemolithotrophs and chemoorganotrophs
• Chemolithotrophs: remove electrons from inorganic substances (hydrogen gas, hydrogen sulfide, sulfur, iron) and combine them with CO₂ and hydrogen
• Chemoorganotrophs: use organic compounds for energy and inorganic compounds as a carbon source
• Lithoautotrophs: rely entirely on inorganic materials for their energy and carbon source

Photosynthetic Bacteria

• Prokaryotic organisms, lack a nucleus, chloroplasts, and other organelles found in plants and algae
• They have a double outer cell membrane and folded inner thylakoid membranes for photosynthesis
• Contain pigments like phycoerythrin and phycocyanin
• They are anoxygenic, meaning they don't produce oxygen
• Absorb light using bacteriochlorophyll, which absorbs shorter wavelengths of light compared to chlorophyll
• Able to live in deeper water where oxygen is absent

Methanogens

• Chemoautotrophs that produce methane from hydrogen gas and carbon dioxide
• Form in anaerobic, hydrogen-containing microenvironments
• They are archaea microorganisms
• Live in ocean vents and hot springs
• Methane can be used as a fuel and acts as a greenhouse gas

Heterotrophs and Their Energy Sources

• Chemoheterotrophs: derive both carbon and energy from organic molecules, process these molecules through respiration or fermentation to produce ATP
• Saprobes: free-living microorganisms that feed on dead organic matter, important in recycling organic materials
• Parasites: obtain nutrients from living hosts, causing harm to the host

Saprobic Microorganisms

• Decomposers of plant litter, animal matter, and dead microbes
• Important in recycling organic materials
• Most saprobes release enzymes to break down food into smaller particles

Parasitic Microorganisms

• Live on or in the body, causing harm to the host
• Considered pathogens because they can damage tissues and cause death
• Ectoparasites: live on the body
• Endoparasites: live in organs and tissues
• Intracellular parasites: live within cells
• Obligate parasites: unable to live outside a living host

The Movement of Molecules: Diffusion and Transport

• Diffusion: the movement of molecules from an area of high concentration to an area of low concentration
• Diffusion across a cell membrane is determined by the concentration gradient and the permeability of the substance

The Movement of Water: Osmosis

• Osmosis: the movement of water across a selectively permeable membrane from a region of high water concentration to a region of low water concentration

Osmosis Conditions

• Isotonic Conditions: equal solute concentration inside and outside the cell, water moves at the same rate in both directions, the most stable environment for cells
• Hypotonic Conditions: lower solute concentration outside the cell, water moves into the cell, cells without walls can swell and burst
• Hypertonic Conditions: higher solute concentration outside the cell, water moves out of the cell, cells may shrink

Adaptations to Osmotic Variations

• Isotonic Environments: pose little stress on cells
• Hypertonic Environments: cells must restrict water loss or increase internal salinity, halobacteria absorb salt to maintain isotonicity
• Facilitated Diffusion: mediated transport utilizing carrier proteins that bind specific substances
• Saturation: the rate of transport is limited by the number of binding sites on transport proteins
• Competition: two molecules with similar shapes can compete for the same binding site on a carrier protein

Transport Processes in Cells

• Active Transport: transports nutrients against a concentration gradient or with a faster rate, requires energy (ATP)
  • Permeases and pumps: membrane proteins involved in active transport
• Endocytosis: the transport of large molecules, particles, or liquids across the cell membrane by certain eukaryotes, requires energy
  • Phagocytosis: cell engulfs whole cells or large solid matter
  • Pinocytosis: entry of oils or molecules in solution into the cell

Environmental Factors That Influence Microbes

• Heat
• Cold
• Gases (O₂, CO₂, N₂)
• Acid
• Radiation
• Osmotic pressure
• Hydrostatic pressure
• Other microbes

Temperature

• Minimum temperature: lowest temperature for growth and metabolism
• Maximum temperature: highest temperature for growth and metabolism, above this enzymes and nucleic acids can denature
• Optimum temperature: intermediate temperature that promotes the fastest rate of growth and metabolism

Temperature Classification

• Psychrophiles (cold): optimal temperature below 15°C, capable of growth at 0°C
• Mesophiles: optimal temperature between 20–40°C, includes most medically significant organisms
• Thermophiles: optimal temperature above 45°C, live in hot environments

Gases (O₂, CO₂, N₂)

• Microbes are categorized by their oxygen requirements:
  • Aerobes: use gaseous oxygen in their metabolism
    • Obligate aerobe: require oxygen for growth
  • Facultative anaerobes: can use oxygen but can also grow without it
  • Microaerophile: require low oxygen concentration
  • Anaerobes: cannot use oxygen and may be harmed by it
    • Strict or obligate anaerobes: cannot tolerate oxygen
  • Aerotolerant anaerobes: do not use oxygen but can tolerate it

Capnophiles

• Grow best in a higher CO₂ tension than is normally present in the atmosphere

pH

• Obligate acidophiles: require an acidic environment for growth
• Alkalinophiles: live in hot pools and soils with high levels of basic minerals

Osmotic Pressure

• Obligate Halophiles: require high concentrations of salt for growth
• Facultative halophiles: resistant to salt, even though they do not normally reside in high-salt environments

Radiation

• Protective measures against radiation:
  • Yellow carotenoid pigments: absorb and dismantle toxic oxygen
  • Enzymes: overcome the damaging effects of UV radiation on DNA

Hydrostatic Pressure

• Barophiles: microbes adapted to high pressures, found in deep sea environments

Associations Between Organisms

• Symbiosis: two organisms living together in a close partnership
• Mutualism: organisms live in an obligatory but mutually beneficial relationship

Test your knowledge on microbial nutrition, including essential nutrients, macronutrients, and micronutrients. Explore the differences between heterotrophs and autotrophs, and understand their carbon sources. This quiz covers the fundamental concepts necessary for understanding microbial growth and metabolism.