Humans And The Ecology Of Bacteria And Viruses Flashcards
what are bacteria?
microscopic unicellular living organisms
-> most > 0.5 < 5m0 um w/ no organelles
what are viruses?
they are microorganisms )< 0.2um) with no capacity to generate their own energy
what do viruses lack?
complete set of RNA
What virus is an exception in terms of size?
mimivirus - large DNA phage
what environments can support bacterial growth?
almost every one, even extreme ones
what are the 6 main characteristics of bacteria?
- self feeding
- self replication
- differentiation (sporulaton)
- chemical signaling
- movement
- evolution
describe autotrophic organisms
use energy from light or chemical oxidation. gets carbon from co2 or cabonate
describe heterotrophic organisms
energy from oxidation of organic molecules, carbon from metabolic intermediates
most pathogens are….
heterotrophic
what does liebigs law state?
growth is not controlled by the total amount of resources available, but the scarcest resource (limiting factor)
what is a real world example of liebigs law?
plant growth often is not limited by water or sunlight, but by nitrogen or phosphate in the soil
what did liebig wrongly think about nitrogen?
he thought that plants assimilated N via gaseous ammonia in a similar fashion to how they do CO2 via photosynethsis
what was proven about how plants assimilate N?
do so as mineral NH4 or NO3-
what was martin’s experiment?
Experiment in which they introduced varying levels of iron to the natural environment & observed increased photosynthetic productivity (via chlorophyll)
what did martin’s experiment find?
the limiting factor was iron, when Fe was added plants grew more
-> increased production of chlorophyll
how does iron act as a limiting factor?
is critical for several metalloproteins in the body, and several bacteria have evolved iron carriers to take advantage of ferric iron in the body
what are siderophores?
Small, high-affinity iron-chelating compounds secreted by microorg’s that serve to transport iron across cell membranes.
-> have high affinity to iron
what has a great # of spiderophores?
e coli
how do siderophores work
Hydroxamate group of molecule binds to ferric iron, Fe3+ (not soluble at neutral pH) –> Ferric hydroxamate. Binds to cytoplasmic receptor on bacteria –> Brought into bacterial cell. Reduction process –> Fe2+. Hydroxamate leaves cytoplasm.
Fe2+ converted into Ferredoxin, then Heme (via Porphyrin)
what are the 2 principles constraining liebigs law?
- Only applicable under steady-state conditions (non-transitioning ecosystem)
- Limiting factor may change according to interaction of environmental variables
what does shelfords law stipulate?
Success of an organism relies not only on the availability of nutrient but also that organism’s tolerance to the environment. Optimal and minimal conditions exist.
optimum growth
the range of physical factors that allow max growth of a given organism
what differentiates eurytypic and stenotypic organisms?
Eury: grow within a wide range of a specific condition (ex: temp)
Steno: grow only in a narrow range of a specific condition (ex: dont tolerate change in temp)
what is meant by quorum sensing
cells reach a certain density and can start expressing proteins which affect surrounding population
what is meant by diauxic growth?
cells grow in 2 phases, caused by the organism switching from one nutrient source to another more beneficial one
what are 4 examples of environments that might affect bacteria growth?
water, sodium, light, temperature
The discovery of what process of chemical reduction of what form of nitrogen led to the used of chemical fertilizer in agriculture?
Discovery of the Haber-Bosch process of chemical reduction of N2 to NH3
enterobactin
a high affinity siderophore that acquires iron for microbial systems.
- Is primarily found in Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium.
what is the most important factor for life on earth
water
water availability and prokaryotes
some have developed molecular adaptations to support low availability of water
what decreases water activity
salt and sugar
resistance to water stress order
staph > pseudo, vibrio > strep, escherichia
Example of S. aureus vs. E. coli as a halotolerant or euryhaline organism
S. aureus can support higher ccn of sodium than E. coli.
Therefore, S. aureus is euryhaline or halotolerant compared to E. coli, which is stenohaline or non-halophile
Non-halophile vs. Halotolerant vs. Halophile vs. Extreme halophile (diagram)
importance of light
- energy source
- direct source of energy
- indirect source of energy
- source of UV rays
- drives thermal processes
- sterilization
in what 3 ways does temperature affect the growth and survival of organisms?
- rate of chemica rxns
- denaturation of proteins
- climate
different enzymes may have varying ______ to _____
tolerance, temperature changes
what is an example of temp and its effects on rate of chemical rxn’s?
- can lead to greater accumulation of certain by-product
- increased N2O from denitrifying bacteria at low temperatures
what are high temperatures usually assocaited with?
geothermal activities in hot springs, hydrothermal vents, or volcanoes (solfarata)
what temperatures can no phototrophic organisms grow at?
temps > 73 degrees
what can grow at temperatures above 73 degrees?
chemolithotrophic bacteria, those who use sulfide, elemental sulfur or ferrous iron as energy source
what adaptations to prokaryotes have to avoid inactivation of proteins are high temperature?
- subtle changes in hydrophobic interactions, H bonds
- extra salt bridges
at what temps do mesophilic bacteria thrive?
~39C
at what temperatures do thermophilic bacteria thrive?
~60C
what temperatures do hyperthermophilic bacteria thrive?
~88C or even greater (108C)
what temperature range do pathogenic bacteria usually prefer?
mesophiles who prefer narrow range of ~37C (normal temp of human body)
e. coli and temperature constraints
e coli OH157:H7 need environment below 25C while retinaing competitiveness at 37C
-> usually grows less at 20C than 37C (challenge for survival)
what kind of bacteria can use a temperature switch?
francisella tularensis in the development of a vaccine
obligate aerobe
organism that requires a constant supply of oxygen in order to live
Performs aerobic respiration
e.g. Micrococcus luteus (commensal)
Typically found on the skin
facultative aerobe
organism that can live with or without oxygen, but has optimal growth w/ oxygen
Can perform aerobic/anaerobic respiration or fermentation
e.g. Escherichia coli
Often found in mammalian sm intestine
microaerophilic aerobe
Oxygen is required but at levels lower than atmospheric (20%) - typically 5%
Perform aerobic respiration
e.g. Magnetospirillum magnetotacticum
Often found in sediment/soil in environment
aerotolerant anerobes
do not utilize oxygen but can survive and grow (less optimally) in its presence
Typically undergo fermentation
e.g. Streptococcus pyogenes (–> Strep throat)
Can be found in upper respiratory tract
e.g. Clostridium dittani
obligate anaerobes
Oxygen is harmful or lethal to them
Can perform fermentation or anaerobic respiration
e.g. Methanobacterium formicicum
Can be foundn in anoxic lake sediment, sewage sludge, etc.
what did oxygen appear
~2 billion years ago