Module 3: Microbe Nutrition

Binary fission

bacterial duplication

Steps: parent cells enlarge → chromosomes duplicate → cell envelope pulls together in cell center and forms septum → cells divide into 2 identical daughter cells

Generation time

also known as doubling time, time required for one fission cycle

length of generation time = organisms growth rate

Stages in microbe growth curve

Lag phase: period of adjustment, enlargement, and synthesis where there’s no growth

Exponential phase: max growth rate

Stationary phase: cell birth rate is equal to cell death rate, decrease in nutrients and oxygen with increase in waste

Death phase: cells die exponentially due to large increase in waste

Essential nutrient

required by an organism, two types: macronutrient and micronutrient

Macronutrients

nutrients needed in large quantities

Micronutrients

also known as trace elements, nutrients needed in smaller amounts

Inorganic nutrients

simple molecule containing atoms other than carbon and hydrogen

Organic nutrients

contains carbon and hydrogen atoms, product of living things

Heterotroph

“other-feeder”, must obtain carbon in organic form so they are dependent on other life forms

Autotroph

“self-feeder”, carbon source is inorganic CO2, not dependent on other living things

Phototroph

energy obtained from photosynthesis(light)

Chemotroph

energy obtained from chemical compounds

Photoautotrophs

carbon source is inorganic compounds, energy source is the sun, produces organic molecules that can be used by them and heterotrophs

Chemoautotrophs

carbon source is inorganic, energy source is inorganic compounds

Lithoautotrophs: rock eaters, rely only on inorganic materials

Methanogens: produce methane from H2 and CO2, formed in anaerobic environments, all are archaea

Photoheterotrophs

carbon source from CO2 and organic compounds from environment, energy from light

Chemoheterotrophs

carbon and energy source from organic molecules which are processed through respiration or fermentation

most bacteria, fungi, protozoa, and animals

Saprobic microbes

free-living and decompose plants, animals, and microbes and most have a rigid cell well and cannot engulf large particles so they release enzymes into the environment to digest stuff then transport into cell

bacteria and fungi

Parasites

derive nutrients from host, live on or in living body of host and cause harm

consider pathogens because they damage tissues and sometimes cause death

Passive transport

no energy required

Simple diffusion

passive transport, movement of molecules down their concentration gradient

Facilitated diffusion

passive transport, molecules move through membranes by receptor down the concentration gradient

Active transport

requires energy, moves molecules against concentration gradient

Endocytosis

large molecules, particles, or liquids cross the cell membrane

Phagocytosis: ingestion of whole cells or large particles; amoebas and certain white blood cells

Pinocytosis: ingestion of liquids

5 environmental factors influencing microbes

temperature, gases, pH, osmotic pressure, and radiation

Cardinal temperatures

range of temp for a microbial species

Minimum: lowest temp permitting microbe to grow and metabolize, below this temp limits the microbes activities

Maximum: highest temp permitting microbe to grow and metabolize, slightly above this temp and protein denaturation in microbes start to occur

Optimum temperature

fastest growth and metabolism of microbe, small chemical differences in bacteria membranes allow survival at different temps

Psychrophiles

cold loving bacteria, below 15 degrees C, can grow at 0 degrees C

Psychrotrophs

feed on the cold, range is 5-35 degrees C

Mesophiles

optimum temp range include the temp of human body, these are most human pathogens

Themoduric

bacteria that can survive short exposure to high temps, common contaminants of heated or pasteurized foods

Thermophiles

heat loving bacteria, optimum temp is >45 degrees C, live in soil and water associated with volcanic activity, compost piles, and sun-exposed habitats

Extreme thermophiles

can be in temps up to 80 degrees C

Aerobes

use gaseous oxygen in metabolism

Obligate aerobes

cannot grow without oxygen

Facultative aerobes

does not require oxygen and can exist without it, if oxygen is present they use aerobic respiration and if oxygen isn’t present they use fermentation

Microaerophile

requires small amount of oxygen, will not grow in atmosphere because there’s too much oxygen

grows in soil, water, and human body

Anaerobes

lack metabolic enzyme systems for using oxygen in respiration

Strict or obligate anaerobes

cannot tolerate free oxygen and will die if its present

live in water, soil, and deep puncture wounds

Aerotolerant

do not use oxygen, can survive and grow in its presence

Capnophiles

grow best at a high CO2 concentration, human body is a good environment for these bacteria to grow due to how much CO2 the body produces

Obligate acidophiles

require acidic environment, molds and yeasts spoil pickled food

Alkalinophiles

require alkaline environments

live in hot pools and mineral-rich soil

Osmotic pressure

tendency of a H2O to move in the direction of lower H2O concentration

How cells protect against osmotic pressure

making a higher solute concentration inside cell, modifying the cell wall such as adding layers of glycoprotein

Halophiles

salt loving bacteria

Obligate halophiles

require high salt environments, have significantly modified cell wall and membranes

Facultative halophiles

can resist salt but are not normally put in conditions where they have to

Osmotolerant halophiles

can grow at relatively high salt concentrations

Protective measures against radiation

yellow carotenoid pigments absorb and dismantle toxic oxygen, enzymes made to overcome the damaging effects of UV radiation on DNA

Symbiosis

two different species living together in a close nutritional partnership, the relationship is required by one or both partners

Mutualism

type of symbiosis where species live in obligatory but mutually beneficial relationships

Commensalism

a type of symbiosis where one species benefits while the other receives neither benefits or harm

Satellitism

type of commensalism where one species provides nutritional or protective factors needed by other species, only for bacteria

Parasitism

type of symbiosis where host provides the parasite with nutrients and habitat where the parasite harms the host to some extent

Synergism

non-symbiotic interaction, two or more free-living species associate where it benefits both but are not necessary for survival, cooperate to produce a result neither could achieve alone

Antagonism

non-symbiotic relationship, arises through competition, common in soils where communities compete for space and food

Antibiosis

example of antagonism, production of inhibitory compounds(antibiotics)

Biofilms

mixed communities(species) of bacteria and other microbes, pioneer colonizer attaches to surface and secretes polymeric or protein substances and other microbes attach to this

Quorum sensing

part of biofilms, cells release chemicals as the population grows to monitor its size

Structure of Biofilms

large complex community with different physical and biological characteristics, partnership among multiple microbial species, change environment to their growth advantage, cannot be eradicated by traditional methods(antibiotics, WBC)