xenobiotics pt 2

Question 1

Bioaugmentation

Answer 1

Addition of pre-adapted bacterial species and communities
Introduction of genetically-modified bacteria
Introduction of biodegradation genes via vectors

Question 2

Biostimulation

Answer 2

Biostimulation

Addition of fertiliser
Surfactants
Removal of competition

Question 3

Antibiotics in the aquatic environment may raise a number of concerns:

Answer 3

Contamination of water
Potential to accelerate evolution of antibiotic resistance
Negative impacts on bacteria performing important ecosystem functions (see graph below)

Question 4

Relatively high concentrations of antibiotics may be released into the environment via sewage and effluent

Answer 4

30 – 90% of administered dose of most antibiotics is excreted as the active form.

Question 5

Co-selection of antibiotic and metal resistance

Answer 5

There is growing concern that metal contamination functions as a selective agent in the proliferation of antibiotic resistance. Documented associations between the types and levels of metal contamination and specific patterns of antibiotic resistance suggest that several mechanisms underlie this co-selection process.

Metal contamination, therefore, represents a long-standing, widespread and recalcitrant selection pressure with both environmental and clinical importance that potentially contributes to the maintenance and spread of antibiotic resistance factors.

Question 6

Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study

Answer 6

Resistance to Colistin found in resistance in a fifth of animals tested, 15% of raw meat samples and in 16 patients

New mutation in MCR-1 gene has spread to E.coli, Klebsiella pneumoniae and Pseudomonas aeruginosa.

Resistance has spread to Laos and Malasya
Possible reason: veterinary use of antibiotics

Huge impact on expected mortality over the next 3 decades

Discovery of new antibiotics far too slow

Question 7

Herbicides

Answer 7

Weeds (34%) have potential to cause greater crop losses than both pests (18%) & diseases (16%)
In the UK, herbicides applied to 20m ha land each year
Can cause contamination of drinking water and impacts on non-target organisms
The first commercially released GMOs were resistant to herbicides

Question 8

glyphosate resistant crop

Answer 8

The massive adoption of glyphosate resistant crops, reduced tillage and over-reliance on glyphosate have resulted in unparalleled selection pressure for glyphosate resistance

Question 9

Mechanisms of evolved resistance to herbicides

Answer 9

1. herbicide application, leading to reduced uptake
2. enhanced metabolism (detoxififcation)
3. sequestration
4. reduced translocation
5. insensitive target site

Question 10

Mechanism of resistanceGlyphosate resistance in Eleusine indica

Answer 10

Resistance is conferred by a single nucleotide substitution resulting in the substitution of proline for serine at amino acid residue 106

Question 11

mechanism of resistance gene amplification

Answer 11

A. Wild type with single copy of EPSPS gene

B. Evolved Amaranthus palmeri with mutiple EPSPS copies

Question 12

what is the relationship between the intensity of the stress (concentration, dose, frequency, rate of change) and the potential for adaptation/evolution?

Answer 12

applied dose of pesticides
 administered dose of an antibiotic
 Environmental dose of an antibiotic
 rate of environmental change
 ecological resilience

Question 13

is there a cost of adaptation?

Answer 13

management of resistance

trade-offs and resource allocation theory

Question 14

high herbicide dose

Answer 14

Resistance can only evolve as a result of selection of novel mutations at ‘major’ genes
Monogenic
response

Question 15

Low herbicide dose

Answer 15

Resistance can evolve as a result of selection and reassortment of ‘standing’ genetic variation
Polygenic
response

Question 16

The cost of resistance:

Answer 16

adapting to a new environment or stress will usually mean that an organism is less fit in the original environment.
The topology of the fitness landscape may be very different in environments with and without herbicide. A peak in a + herbicide environment may be trough in a herbicide-free environment