L3 - Microbial Metabolic Abilites

Question 1

What is a big molecule that’s a problem and what are its features?

Answer 1

Lignin
2nd most abundant polymer after cellulose
amorphous structure very difficult for microbes to get at
Waste product of paper industry

Question 2

What are other big molecules of polymers and eg?

Answer 2

PAHs - poly-aromatic-hydrocarbons

e.g. anthacene, pentacene

Question 3

Why are PAHs a problem?

Answer 3

Several rings linked together difficult to break apart

Question 4

What are two toxic organics?

Answer 4

Cyanides, Phenol

Question 5

What are the features of the toxic organics - cyanides?

Answer 5

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

Question 6

What are the features of the toxic organic phenol?

Answer 6

Disrupts membranes

Used as an antimicrobial

Question 7

Example of a highly toxic inorganic?

Answer 7

Methylmercury acts as a neurotoxin

Question 8

What are problems microbes face in bioremediation?

Answer 8

Physically getting at pollutant
How to get it into cell
How to survive in its presence
How to get energy or carbon

Question 9

How do microbes get at large molecules?

Answer 9

Produce extracellular enzymes
A range of oxidative enzymes such as peroxidases, endo and exocellulases
Produce free radicals that randomly break bonds (smash and grab)

Question 10

How can microbes get to water insoluble compounds like oil?

Answer 10

Use of biosurfactants eg glycolipids, phospholipids, lipoproteins

Question 11

How do biosurfactants work?

Answer 11

Migrate to interface of water and oil (hydrophobic side towards oil).
Redcues interfacial tension allowing greater mixing
Formation of micelles
Pseudo-solubilises the oil

Question 12

How do microbes get oil into their cell?

Answer 12

Direct uptake - microbes attach to droplets of oil emulsified by surfactants

Question 13

How do cells perform pseudo- stabilisation/solubisation?

Answer 13

Hydrophobic compartments on cell wall of some yeasts - alkane/surfactant complex dissociates within this

Question 14

What are examples of processes used by microbes to detoxify toxic compounds?

Answer 14

Hydrolysis
Hydroxylation
Demethylation
Methylation
Dehalogenation

Question 15

What is dehalogenation and what is it used on?

Answer 15

Taking off a chlorine

Pesticides and industrial wastes are chlorinated

Question 16

What is the main definition of biodegradation?

Answer 16

The conversion by biological agencies of a complex organic material into one or more simpler substances.

Question 17

What is crude oil made up of?

Answer 17

75% hydrocarbons
25% nitrogen, oxygen, sulphur
Small proportion metallic compounds

Question 18

What are the features of the hydrocarbons alkanes?

Answer 18

Straight of branched chains

Vary in length from one carbon to 20+

Question 19

What are the features of the hydrocarbons alicyclics?

Answer 19

One of more rings

Question 20

What are the features of the hydrocarbons alkenes?

Answer 20

Unsatured straight or branched chains with some double bonds between carbon atoms

Question 21

Why is hydrocarbon degradation by microbes possible?

Answer 21

Compounds found in oil can be considered analogous to compounds found in natural environment

Question 22

What are examples of aromatics?

Answer 22

Benzene, phenol, anthracene

Question 23

What is the process of alkane degradation?

Answer 23

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

Question 24

What is the process of aromatic degradation?

Answer 24

• 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

Question 25

Define recalcitrance

Answer 25

The ability of a substance to remain in a particular environment in an unchanged form

Question 26

What are the two categories of recalcitrant compounds?

Answer 26

High molecular weight polymers and polycylic aromatics

Low molecular weight substituted hydrocarbons

Question 27

Why are Low molecular weight hydrocarbons recalcitrant?

Answer 27

Toxicity

Question 28

Why are high MW hydrocarbons recalcitrant?

Answer 28

Inaccessibility of substrate to microbial enzymes

Question 29

What are conditions that affect biodegradation?

Answer 29

Microbial pop
Structure
Toxicity
Temp
pH
SA
Oxygen
Water

Question 30

What are levels of oxygen dependant on?

Answer 30

Microbial oxygen consumption
Type of envi (clay soils less permeable)
Avail of utilisable substrates increasing microbial depletion

Question 31

How does temp affect degredation?

Answer 31

Optimal temp for oil is 30-40
Reported as low as 3
Decreases in temp decreases enzymatic activity by Q10 effect (value 1-3)

Question 32

How does pH affect degredation?

Answer 32

Most good at neutral

Fungi more tolerant to acidic

Question 33

How does inorganic nutrient avail affect degradation?

Answer 33

N, P, K, S , Mg, Ca and Fe required for growth and metabolism
C rich pollution depletes N and P

Question 34

How do cometabolites work?

Answer 34

Easily metabolised substrate could enhance rate of degradation of recalcitrant molecules