导图社区 Chapter 7 - Microbial nutrition
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Chapter 7 - Microbial nutrition
英语微生物学思维导图
编辑于2022-02-24 16:10:33
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Microbial nutrition
Nutrients for growth
Nutrition: process by which chemical substances are acquired from the environment and used in cellular activities
how to get carbon?
heterotroph: must obtain carbon in an organic form
autotroph: obtain carbon in an inorganic form (e.g. CO2, carbonate) - not nutritionally dependent on other living things
how to get energy?
chemotroph: gain energy from chemical compounds
phototroph: gain energy through photosynthesis
radiation: Candidatus Desulforudis audaxviator*
nutritional categories
Photoautotroph - photosynthetic organisms, such as algae, plants, cyanobacteria
chemoautotroph - certain bacteria, such as methanogens, deep-sea vent bacteria
chemoheterotroph
normal: metabolic conversion of the nutrients from other organisms, such as protozoa, fungi, many bacteria, animals
saprobe: metabolizing the organic matter of dead organisms, such as fungi, bacteria (decomposers)
parasite: utilizing the tissues, uids of a live host, such as various parasites and pathogens
photoheterotroph - sunlight or organic matter, such as the purple and green photosynthetic bacteria
nutrients
essential nutrients： must be provided to an organism
macronutrients: required in large quantities; play principal roles in cell structure and metabolism; (e.g. proteins, carbohydrates)
micronutrients (trace elements): required in small amounts, involved in enzyme function and maintenance of protein structure; (e.g. zinc, nickel, manganese)
organic nutrients: usually the product of living things (e.g. methane, carbohydrates, lipids, proteins, and mucleic acid)
inorganic nutrients: contains a combination of atoms other than carbon and hydrogen (e.g. metals and their salts, gases and water)
chemical analysis of cell
70% water
proteins
96% - CHONPS
Transport
passive transport (does not need energy)
diffusion - substances exist in a gradient and move from across of higher concentration toward areas of lower concentration
osmosis - diffusion of water, toward the solute
with cell wall
isotonic solution - water concentration is equal on each side, the rates of diffusion are equal in both directions
hypotonic solution - net diffusion of water into the cell, swells the protoplast and pushes it against the cell wall
hypertonic solution - net diffusion of water out of the cell and shrinlds the protoplast (plasmolysis)
without cell wall
isotonic solution - rates of diffusion are equal in both directions
hypotonic solution - diffusion of water into the cell causes it to swell, and may burst (osmolysis)
hypertonic solution - water diffusing out of the cell causes it to shrink and become distorted
facilitated diffusion - requires a carrier
active transport
active transport - requires a carrier, energy (electrochemical potential/ATP)
group translocation - transported molecule chemically altered
bulk transport
endocytosis - bringing substances into the cell through a vesicle or phagosome
pinocytosis - ingests liquids
phagocytosis - ingests substances or cells
exocytosis - vice versa
Factors on growth
niche: totality of adaptations organisms make to their habitat
environmental factors affect the function of metabolic enzymes
factord include:
temperature
minimum temperature - lowest temperature that permits a microbe's growth and metabolism
maximum temperature - highest temperature that permits a microbe's growth and metabolism
optimum temperature - promotes the fastest rate of growth and metabolism
3 temperature adaptation groups
psychrophiles - optimum temperature < 15, capable of growth at 0
mesophiles - optimum temperature 20~40
thermophiles - optimum temperature greater than 45
gas requirements
oxygen
oxygen will be transformed into several toxic products
singlet oxygen
superoxide ion
peroxide
hydroxyl radical
most cells have enzymes that neutralize these chemicals
superoxide dismutase
catalase
if a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats
categories of oxygen requirement
aerobe - ultilizes oxygen and can detoxify it
obligate anaerobe - can not grow without oxygen
microaerophilic - requires only a small amount of oxgen
facultative anaerobe - utilizes oxygen but can also grow in its absence
anaerobe - does not utilize oxygen
obligate anaerobe - lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment
aerotolerant anaerobe - do not utilize oxygen but can survive and grow in its presence
carbon dioxide
all microbes require some carbon dioxide in their metabolism
capnophile: grows best at higher CO2 tensions than normally present in the atomosphere
pH
neutrophile - majority of microorganisms grow at a pH between 6 and 8
acidophile - growth at extreme acid pH
alkalinophile - grow at extreme alkaline pH
osmotic pressure
most microbes exist under hypotonic or isotonic conditions
halophile: require a high concentration of salt
osmotolerant: do not require high concentration of solute but can tolerate it when occurs
barometric pressure
barophiles: can survive under extreme pressure and will rupture if exposed to normal atmospheric pressure
Ecological Associations
symbiotic - organisms live in close nutritional relationships, required by one or both members
mutualism - obligatory, dependent, both members benefit
commensalism - the commensal benefits, other member not harmed
parasitism - parasite is dependent and benefitd, host harmed
nonsymbiotic - organisms are free-living, relationships not required for survival
synergism - members cooperate and share nutrients
antagonism - some members are inhibited or destroyed by others (antibiosis)
interrelationships between microbes and humans
human body is rich habitat for symbiotic bacteria, fungi, and a few protozoa - normal microbial flora
commensal, parasitic, and synergistic relationships
microbial biofilms
biofilm formation - organisms attach to a substrate by some form of extracellular matrix that binds them togetther in complex organized layers
dominate the structure of most natural environments on earth
quorum sensing - communicate and cooperate in the formation and function of biofilms
Microbial growth
two levels: growth at a cellular level with increase in size, and increase in population
binary fission (transverse)
parent cell enlarges, duplicates its chromosome and forms a central transverse septum dividing the cell into two daughter cells
rate of population growth
generation/doubling time - time required for a complete fission cycle
exponential growth - each new fission cycle increases the population by factor of 2
generation times vary from minutes to days
the population growth curve
Lag phase - "flat" period of adjustment, enlargement, little growth
exponential growth phase - a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment
stationary phase - rate of cell growth equals rate of cell death caused by depleted nutrients and oxygen, excretion of organic acids and pollutants
death phase - as limiting factors intensify, cells die exponentially
methods of analyzing population growth
turbidometry: most simple
degree of cloudiness, turbidity, reflects the relative population size
measures 3 phases: Lag, Log and stationary, can't tell dead cells from live cells
a non-viable count or indirect count
enumeration of bacteria
viable plate count
direct cell count - count all cells present; automated or manual (hemocytometer)