L3 - Microbial Metabolic Abilites Flashcards
What is a big molecule that’s a problem and what are its features?
Lignin
2nd most abundant polymer after cellulose
amorphous structure very difficult for microbes to get at
Waste product of paper industry
What are other big molecules of polymers and eg?
PAHs - poly-aromatic-hydrocarbons
e.g. anthacene, pentacene
Why are PAHs a problem?
Several rings linked together difficult to break apart
What are two toxic organics?
Cyanides, Phenol
What are the features of the toxic organics - cyanides?
Range of compounds containing C=-N
Commonly form at former gas works
Inhibits electron transport chain so doesn’t affect fermentative growth in anaerobic conditions
What are the features of the toxic organic phenol?
Disrupts membranes
Used as an antimicrobial
Example of a highly toxic inorganic?
Methylmercury acts as a neurotoxin
What are problems microbes face in bioremediation?
Physically getting at pollutant
How to get it into cell
How to survive in its presence
How to get energy or carbon
How do microbes get at large molecules?
Produce extracellular enzymes
A range of oxidative enzymes such as peroxidases, endo and exocellulases
Produce free radicals that randomly break bonds (smash and grab)
How can microbes get to water insoluble compounds like oil?
Use of biosurfactants eg glycolipids, phospholipids, lipoproteins
How do biosurfactants work?
Migrate to interface of water and oil (hydrophobic side towards oil).
Redcues interfacial tension allowing greater mixing
Formation of micelles
Pseudo-solubilises the oil
How do microbes get oil into their cell?
Direct uptake - microbes attach to droplets of oil emulsified by surfactants
How do cells perform pseudo- stabilisation/solubisation?
Hydrophobic compartments on cell wall of some yeasts - alkane/surfactant complex dissociates within this
What are examples of processes used by microbes to detoxify toxic compounds?
Hydrolysis Hydroxylation Demethylation Methylation Dehalogenation
What is dehalogenation and what is it used on?
Taking off a chlorine
Pesticides and industrial wastes are chlorinated
What is the main definition of biodegradation?
The conversion by biological agencies of a complex organic material into one or more simpler substances.
What is crude oil made up of?
75% hydrocarbons
25% nitrogen, oxygen, sulphur
Small proportion metallic compounds
What are the features of the hydrocarbons alkanes?
Straight of branched chains
Vary in length from one carbon to 20+
What are the features of the hydrocarbons alicyclics?
One of more rings
What are the features of the hydrocarbons alkenes?
Unsatured straight or branched chains with some double bonds between carbon atoms
Why is hydrocarbon degradation by microbes possible?
Compounds found in oil can be considered analogous to compounds found in natural environment
What are examples of aromatics?
Benzene, phenol, anthracene
What is the process of alkane degradation?
1 - mono-oxygenase enzymes put on oxygen to produce alcohol
2 - alcohol dehydrogenated to yield an aldehyde
3 - Aldehyde oxidised into a fatty acid
4 - Fed in to B oxidation pathway yielding Acetyl CoA
What is the process of aromatic degradation?
- Key step is opening stable ring structure to give aliphatic intermediates
1 - oxidation of aliphatic side chain into carboxylic acid or demethylation
2 - put 2 adjacent hydroxyl (OH) groups on aromatic ring by mono or dihydroxylation
3 - orthocleavage between hydroxyls
Define recalcitrance
The ability of a substance to remain in a particular environment in an unchanged form
What are the two categories of recalcitrant compounds?
High molecular weight polymers and polycylic aromatics
Low molecular weight substituted hydrocarbons
Why are Low molecular weight hydrocarbons recalcitrant?
Toxicity
Why are high MW hydrocarbons recalcitrant?
Inaccessibility of substrate to microbial enzymes
What are conditions that affect biodegradation?
Microbial pop Structure Toxicity Temp pH SA Oxygen Water
What are levels of oxygen dependant on?
Microbial oxygen consumption
Type of envi (clay soils less permeable)
Avail of utilisable substrates increasing microbial depletion
How does temp affect degredation?
Optimal temp for oil is 30-40
Reported as low as 3
Decreases in temp decreases enzymatic activity by Q10 effect (value 1-3)
How does pH affect degredation?
Most good at neutral
Fungi more tolerant to acidic
How does inorganic nutrient avail affect degradation?
N, P, K, S , Mg, Ca and Fe required for growth and metabolism
C rich pollution depletes N and P
How do cometabolites work?
Easily metabolised substrate could enhance rate of degradation of recalcitrant molecules
