Essential nutrient

- Any substance, whether in elemental or molecular for that must be provided to an organism

Macronutrients

- required in relatively large quantities

- play principal roles in cell structures and metabolism

Micronutrients (trace elements)

- present in smaller amounts

- involved in enzyme function (as cofactors) and maintenance of protein structure

Essential Sources I

1. Nitrogen

2. Oxygen

3. Hydrogen

1. component of amino acids, DNA, RNA, and ATP

2. component of carbohydrates, lipids, nucleic acids and proteins

3. (a) maintains pH (b) forms hydrogen bonds between molecules (c) source of free energy in oxidation-reduction of respiration 

Essential Sources II

4. Phosphorous

5. Sulfur

6. Growth factor

4. component of nucleic acids

5. component of vitamins and amino acids methionine and cysteine

6. (a) organic compound that cannot be synthesized by an organism: amino acid, nitrogen base, or vitamin (b) must be provided by the environment (c) versatile bacteria (E. coli) vs. fastidious bacteria

Energy Sources

1. Phototroph

2. Chemotroph

1. microbes that photosynthesize and gain energy from sunlight (Ek)

2. microbes that gain energy from chemical compounds (Ep)

Carbon Sources

Autotroph

- "self-feeder"

- organism that uses inorganic CO2 as its carbon source

- have the capacuty to convert CO2 into carbon compounds

- not dependent on other living things

- energy source = nonliving environment

Carbon Sources

Heterotroph

- an organism that must obtain its carbon in organic form

- dependent on other life forms

- most carbon sources exist in a form that is simple enough for absorption

- many carbon sources must be digested by the cell in order to be absorbed

- energy source = other organisms or sunlight

Photoautotrophs

- energy source = uses sunlight for energy and transforms it into chemical energy that can be used for cell metabolism (Ek→Ep)

- uses inorganic compounds as a carbon source to produce organic molecules that can be used by themselves and heterotrophs

- form the basis of most food pyramids

- examples = photosynthetic organisms, such as algae, plants, cyanobacteria

Chemoautotrophs

- chemoorganic autotrophs: use organic compounds for energy and inorganic compounds as a carbon source

- lithoautotrophs: rely completely on inorganic compounds

- as "eaters of rock" they are responsible for weathering of rocks to form soil, as well as biogeochemical cycling of many elements 

- example = only certain bacteria or archaea, such as methanogens, deep-sea vent bacteria

Photoheterotrophs

- energy source = uses sunlight rays for energy and transforms it into chemical energy that can be used for cell metabolism (Ek→Ep)

- uses organic compounds as a carbon source

- unlike plans, they do not use water as their reducing agent, so they do not produce oxygen. instead, they use H2S, which is oxidized to produce granules of elemental sulfur

- example = purple and green photosynthetic bacteria

Chemoheterotrophs

- energy source = metabolizing the organic matter of dead organisms

- uses organic compounds to derive both energy and carbon

-organic molecules processed through (aerobic or anaerobic) respiration or fermentation to produce ATP (Ep→Ep)

- example = fungi, bacteria (decomposers)

- principal energy-yielding pathway in animals, protozoa, fungi, and aerobic bacteria

→→ glucose and oxygen are reactants, and carbon dioxide is given off

Parasites

- energy source = derive nutrients from the cells or living tissues of a host

- live on or in the body

- pathogens: cause some degree of harm to the host (disease to death)

→→ectoparasites: live on the body

→→endoparasites:  live in organs and tissues

→→intracellular parasites:  live within cells

→→obligate parasites: always cause harm, unable to live outside of a living host

→→facultative parasites:  is opportunistic pathogen in immunocompromised host

- example = various parasites and pathogens; can be bacteria, fungi, protozoa, animals

Saprobes

- free-living organisms that feed primarily on organic detritus from dead organisms

- decomposers of plant litter, animal matter, and dead microbes (important in recycling of organic materials)

- most of these have a rigid cell wall and cannot engulf large particles of food 

- release enzymes into the environment to digest food into smaller particles that can be transported into the cell

- example = fungi, bacteria

How do microbes feed? What is the process of nutrient absorption?

- necessary nutrients must be taken into the cell and waste materials must be transported out of the cell

- transport occurs across the cell membrane

→→structure specialized for transport

→→cell wall is too non-selective to screen the entrance or exist of molecules

- passive transport (simple & facilitated diffusion)

- active transport (carrier-mediated & bulk)

Passive transport

- doesn't need energy; movement down concentration gradient

- simple diffusion: for hydrophobic molecules - small and/or uncharged 

- facilitated diffusion: for hydrophilic molecules - large and/or uncharged

→→for H2O as universal solvent (osmosis)

→→for hydrophilic solutes: salts, monosaccharides

Active transport

- needs energy

- carrier-mediated

→→ion pumps: sodium-potassium pump; proton pump

→→cotransport: needs energy indirectly for H+/sucrose , H+/amino acids, Na+/Glu

- bulk

→→exocytosis: cellular secretion

→→endocytosis: phagocytosis ("cellular eating"), pinocytosis ("cellular drinking")

Simple Diffusion

- movement of molecules in a gradient from an area of higher concentration to an area of lower concentration

- diffusion across a cell membrane is determined by the concentration gradient and the permeability of the substance

Osmosis

- facilitated diffusion of H2O

- the movement of water across a semipermeable (selectively permeable) membrane (has passageways that allow the passage of water but not other substances)

Facilitated Diffusion

- passive transport

- utilizes transport proteins (channel or carrier) that will bind a specific substance 

- binding changes the conformation of the carrier proteins so that the substance is moved across the membrane

Ion pumps

- active carrier-mediated transport

- transports nutrients against a concentration gradient or with a concentration gradient at a faster rate

- presence of specific membrane proteins (pumps) and energy (ATP)

Cotransport

- active carrier-mediated transport

- movement of some large molecules across the membrane via transport proteins 

- needs indirect energy: driven by facilitated diffusion of other molecules (usually H+ or Na+)

- sucrose / H+: couples facilitated diffusion of H+ with the active transport of sucrose (against its concentration gradient)

- amino acid / H+

- glu / Na+ 

Endocytosis

- active bulk transport

- transport of large molecules, particles, or liquids across the cell membrane by certain eukaryotes

- requires the expenditure of energy

- phagocytosis: * by amoebas and certain white blood cells that ingest whole cells or large solid matter

- pinocytosis: entry of oils or molecules in solution into the cell

Effect of Osmosis on cells with/without cell walls

- tonicity: ability of a surrounding solution to cause a cell to gain or lose water

- hypotonic:  low [solute] -- water enters cell

- isotonic: same [solute] -- no net movement of water

- hypertonic: high [solute] -- water leaves cell

Hypotonic Conditions

- solute concentration of the external environment is lower than that of the cell's internal environment

- pure water is the most hypotonic environment because it has no dissolved solutes

- the net direction of osmosis is from the hypotonic solution into the cell

- cells without walls can swell and burst

Isotonic Conditions

- the external environment is equal to the cell's internal environment

- diffusion of water proceeds at the same rate on both sides of the cell

- generally the most stable environments for cells; already in an osmotic steady state with the cell

Hypertonic Conditions

- environment outside of the cell has a slightly higher concentration of solutes than inside the cell

- high osmotic pressure forces water to diffuse out of the cell

- limits the growth of microbes

- principle behind using concentrated salt and sugar solutions to preserve food

1. Obligate aerobes

2. Obligate anaerobes

3. Facultative anaerobes

4. Microaerophiles

5. Aerotolerant anaerobes

1. gather at the top of the test tube in order to absorb maximal amount of oxygen

2. gather at the bottom to avoid oxygen

3. can be found all along the test tube (metabolize by anaerobic respiration / fermentation when oxygen is absent; metabolize by aerobic respiration when oxygen is present

4. gather at the upper part of the test tube but not at the top - require oxygen, but at a lower concentration

5. are evenly spread along the test tube - do not use oxygen but are not affected at all by oxygen

Symbiotic

- organisms live in close nutritional relationships; required by one or both members

- mutualism, commensalism, parasitism

Nonsymbiotic

- organisms are free-living; relationships not required for survival

- synergism, antagonism

1. Mutualism

2. Commensalism

3. Parasitic

1. obligatory. dependent; both members benefit

2. the commensal benefits; other member not harmed

3. parasite is dependent and benefits; host harmed

1. Synergism

2. Antagonism

1. an interrelationship between two or more free-living organisms that benefits both but is not necessary for their survival

2. arises when members of a community compete; one microbe secretes chemical substances into the surrounding environment that inhibit or destroy other microbes; antibiosis:  production of inhibitory compounds, such as antibiotics

Satellitism

- type of commensalism

- one member provides nutritional or protective factors needed by the other

Binary fission

- parent cell enlarges

- chromosomes are duplicated

- cell envelope pulls together in the center of the cell to form a septum

- cell divides into two daughter cells

The Rate of Population Growth

- N(final) = 2n(N initial)

- first N = final # of cells; little n = # of generations; last N = starting # of cells

- the time required for a complete fission cycle

- after each generation, the population doubles in size

- as long as the environment remains favorable, the doubling effect can continue at a constant rate

- average bacterial generation time is 20-60 mins.

Lag phase

- flat period on the graph when the population appears not to be growing

- newly inoculated cells require a period of adjustment, enlargement, and synthesis

Exponential growth or log phase

- period during which the growth curve increases dramatically

- phase will continue as long as cells have adequate nutrient and the environment is favorable

Stationary growth phase

- population enters survival mode

- cells stop growing or grow slowly

Death phase

- limiting factors intensify and cells begin to die at an exponential rate

- curve dips downward