Module 4

Plant Growth Promoting Rhizobacteria (PGPR) and Endophytes

1. PGPR stands for Plant Growth Promoting Rhizobacteria.
2. PGPR enhance plant growth through nitrogen fixation, phosphate solubilization, and hormone production.
3. Examples of PGPR – Azospirillum, Azotobacter, Pseudomonas fluorescens, Bacillus subtilis.
4. Phytohormones produced by PGPR – IAA, GA, Cytokinins.
5. Siderophores – Iron-chelating compounds secreted by Pseudomonas and Bacillus.
6. ACC deaminase enzyme – Reduces plant stress by lowering ethylene levels.
7. Endophytes – Microbes living inside plant tissues without causing harm.
8. Example of bacterial endophytes – Enterobacter, Burkholderia, Bacillus megaterium.
9. Endophytic fungi – Neotyphodium, Piriformospora indica.
10. PGPR inoculation improves seed germination, root length, and yield.
11. Mechanisms of PGPR – Biofertilization, Biostimulation, and Biocontrol.
12. Biofilm formation by rhizobacteria improves colonization and protection.
13. Rhizosphere effect – Zone around roots with intense microbial activity.
14. Rhizosphere soil – Rich in exudates and microbial biomass.
15. Phyllosphere – Microbial habitat on the leaf surface.
16. Endorhizosphere – Microbial community inside root tissues.
17. Rhizoplane – Microbes attached to root surface.
18. PGPR formulation – Used as seed coating, root dipping, or soil drenching.
19. Biopriming – Soaking of seeds in microbial suspension before sowing.
20. Rhizobacteria produce antibiotics like 2,4-DAPG and phenazine against pathogens.

Microbes in Food and Dairy Industry

1. Lactic acid bacteria (LAB) – Convert lactose to lactic acid.
2. Yogurt – Prepared by Lactobacillus bulgaricus and Streptococcus thermophilus.
3. Curd – Contains Lactobacillus acidophilus as major microbe.
4. Cheese – Ripened using Penicillium roqueforti (blue cheese) or Penicillium camemberti (Camembert).
5. Butter and ghee – Fermentation improves flavor and texture.
6. Vinegar – Produced by Acetobacter aceti from ethanol oxidation.
7. Bread making – Saccharomyces cerevisiae (yeast) used for fermentation.
8. Fermented soy products – Rhizopus oligosporus (tempeh), Aspergillus oryzae (soy sauce).
9. Idli and dosa fermentation – Leuconostoc mesenteroides and Streptococcus faecalis.
10. Pickle fermentation – Lactobacillus plantarum.
11. Spoilage of canned foods – Caused by Clostridium botulinum.
12. Botulism toxin – Produced under anaerobic conditions.
13. Food preservation methods – Pasteurization, freezing, irradiation.
14. Pasteurization – Named after Louis Pasteur; used for milk safety.
15. Fermented beverages – Beer, wine (by yeast fermentation).
16. Probiotics – Live beneficial microbes improving gut health (Lactobacillus, Bifidobacterium).
17. Prebiotics – Non-digestible food ingredients promoting probiotic growth.
18. Synbiotics – Combination of probiotics and prebiotics.
19. SPOILAGE indicators – Odor, gas, slime, off-flavor in foods.
20. Mycotoxins – Aflatoxin (Aspergillus flavus), Ochratoxin (Penicillium).

Industrial and Environmental Microbiology

1. Industrial microbiology – Large-scale microbial production of useful products.
2. Fermenters / Bioreactors – Used for industrial fermentation.
3. Batch fermentation – Closed system; product harvested after completion.
4. Continuous fermentation – Nutrients continuously supplied.
5. Submerged fermentation – Microbes grow in liquid medium.
6. Solid state fermentation – Microbes grow on moist solid substrate (e.g., bran).
7. Citric acid – Aspergillus niger.
8. Ethanol – Saccharomyces cerevisiae.
9. Acetone-butanol – Clostridium acetobutylicum.
10. Lactic acid – Lactobacillus delbrueckii.
11. Antibiotic – Penicillin discovered by Alexander Fleming (1928).
12. Streptomycin – Discovered by Selman Waksman (1944).
13. Tetracycline – Produced by Streptomyces aureofaciens.
14. Erythromycin – Saccharopolyspora erythraea.
15. Enzyme – Amylase – Aspergillus oryzae.
16. Enzyme – Protease – Bacillus subtilis.
17. Enzyme – Cellulase – Trichoderma reesei.
18. Single Cell Protein (SCP) – Protein from microbial biomass (Spirulina, Yeast).
19. SCP sources – Chlorella, Spirulina, Candida, Fusarium venenatum.
20. SCP benefits – High protein (60–70%), vitamins, low fat.

Microbes in Environment and Bioremediation

1. Oil spill degradation – Pseudomonas putida, Alcanivorax borkumensis.
2. Bioleaching – Metal extraction using microbes (Thiobacillus ferrooxidans).
3. Biomining – Recovery of metals from ores using microbes.
4. Biodegradation of plastics – Pseudomonas, Aspergillus niger, Ideonella sakaiensis.
5. Composting microbes – Trichoderma, Aspergillus, Bacillus, Actinomycetes.
6. Vermicomposting – Involves Eisenia foetida (red worm).
7. Bioindicator species – Microbes indicating pollution levels.
8. Biosensors – Microbial tools detecting environmental toxins.
9. Phytoremediation – Plants + microbes removing heavy metals.
10. Biogas microbes – Methanobacterium, Methanococcus.
11. Stages of biogas production – Hydrolysis → Acidogenesis → Methanogenesis.
12. Sludge digestion – Stabilization of organic matter by microbes.
13. Biocomposting of agro-waste improves soil carbon and fertility.
14. Microbial degradation of pesticides – Pseudomonas, Flavobacterium.