List three (3) types of synthetic biodegradable plastics and one (1) microorganism capable of their degradation. List 3 types of natural plastics and one (1) microorganism capable of their degradation.

Adheres to moist surface $\rightarrow$ oxidizes S to H$_2$SO$_4$ $\rightarrow$ etches CaCO$_3$ in cement.

Spores germinate on surface $\rightarrow$ hyphae penetrate pores $\rightarrow$ secrete organic acids.

(cyanobacterium/alga)
Photosynthesizes on surface $\rightarrow$ traps moisture/dust $\rightarrow$ produces acids, physical expansion.

Section B (partial from query)

Mechanisms of microbial corrosion of metals (7.5 marks)

Microbial corrosion (MIC) involves:

Microbes (e.g., Thiobacillus) produce H$^+$ or organic acids, lowering pH:

Sulfate-reducing bacteria (Desulfovibrio) consume H$_2$:

Anaerobic zones under biofilm $\rightarrow$ differential aeration cells.

Exopolysaccharides trap corrosive agents, concentrate ions.

Proteases/enzymes degrade passive oxide layers.

6 characteristics of biodeteriogens influencing activity:

1. Enzyme production: Cellulases, ligninases for substrate attack.

2. Adhesion capability: Pili, fimbriae, hydrophobins for surface attachment.

3. Metabolic versatility: Aerobic/anaerobic, use diverse C/N sources.

4. Acid/alkali tolerance: Thrive at pH 2-10.

5. Biofilm formation: Protects from biocides, concentrates nutrients.

6. Spore-forming: Resistant dormant stage for colonization.

Section C

5a. List 3 types of synthetic biodegradable plastics and 1 microorganism capable (4 marks)

1. Polylactic acid (PLA): From corn starch.

2. Polyhydroxyalkanoates (PHA): Bacterial polyester.

3. Polycaprolactone (PCL): Semi-crystalline polyester.

Microorganism: Amycolatopsis orientalis degrades PLA via hydrolases.

5b. Natural plastics and 1 microorganism (4.5 marks)

Natural plastics: Cellulose, chitin, natural rubber (polyisoprene).

Microorganism: Streptomyces coelicolor degrades natural rubber via latex-clearing protein (Lcp).

Final answers bolded above.