Lecture 24 Flashcards
Extracellular polysaccharides
An organic material that is produced by microbes when colonizing surfaces that allows more bacteria to stick to a surface
Biofilm
a film of extracellular polysaccharides (and microbes) that forms composed of only one type of bacteria trying to attach itself to a surface
Microbial mats
thicker microbial films
Microbial mats are ___ and have _____ layers.
thick, segregated
Stromatolite
The lithified version of a microbial mat (upper part is still alive)
Proof that there was microbial life in oceans millions of years ago:
microbial mat
Microbes are sticky and reactive due to
EPC
EPS
Extracellular layers that are located external to the cell wall
Two types of EPS
capsules and sheaths
Capsule EPS
amorphous layered EPS
cheaths
structured layered EPS
Deprotination
Cell walls/ EPS contain molecules that can release protons into the solution
Deprotination leads to the formation of
organic anion or ligand
Most important surface group to microbes
Carboxyls (are most abundant and most important for surface charge)
Why bacteria is used in industrial processes
they are everywhere, reactive, have small surface area to volume ratio, and are good for bonding metals
Bioremediation
bacteria absorb metals meaning they are used in bioremediation strategies
Biosorption
process y which microbial biomass acts as a surface upon which toxic metals and radionuclides are passively absorbed
Bioaccumulation
the metabolic process used by living biomass in which physiologically important metal ions are absorbed by cells
two ways of biomineralization
Biologically induced biomineralization and biologically controlled biomineralization
biologically induced biomineralization
occurs without any regulatory control - biominerals are produced as by-products due to the activity of the microorganism and their surrounding environment
Examples of induced biomineralization
release of metabolic wastes (CO2, OH-, H+, NH3, and H2S). the release of cations by the cell, or the development of a charged surface
Biologically controlled biomineralization
a completely regulated process, allowing the organism to precipitate minerals that serve physiological roles
How induced bioremediation works with EPS
- a metal binds with the cell surface of the microbe (leaving positive change on the outside)
- those metals react with anions from the solution
What is the most likely environment to study old bacteria and why?
Silicified environments - bacteria become encrusted in amorphous silica because they hydrothermal fluids are often very enriched in dissolved silica
examples of microbes that have control over the silification process
diatoms (building of silica shell) and radiolarians
Largest fraction of known biologically controlled biominerals are:
calcium carbonate minerals
Calcium carbonate precipitation occurs from
coccolithophores and foraminifera microorganisms that remove calcium carbonate from seawater to form their skeletons
The most important role of microbes in terms of chemical weathering is the formation of _____ via ____ or ____
carbon dioxide
aerobic respiration or dead organic material
Microbes aerobic respiration equation
glucose+ oxygen —-> 6CO2 + 6H20 (Co2 will react with water later to make carbonic acid)
Microbes accelerate mineral dissolution by:
production of organic acids
Two ways organic acids increase mineral dissolution:
- they release protons to attack minerals directly
2. they lower a mineral’s saturation state by reacting with them
Microbes can make energy through:
chemosynthesis or photosynthesis
Pyrite and microbial processes
Sulfur and iron are in reduced forms, they can be oxidized at the earth’s surface by microbes.
Acid mine drainage
During coal and metal mining operations, waste rocks are disposed of In the form of spoil heaps or in tailings ponds. Those waste materials typically contain residues of pyrite and other sulfide minerals that are unstable upon exposure to oxygenated waters. This results in acidic and sulfate/metal-rich effluent.
Bioleeching
the use of bacteria, to leach minerals such as copper, zinc, uranium, nickel, and cobalt from sulfide minerals.
