The Master 'Microbe -> Product/Role' Table

Almost every hard NEET question in this chapter is a match or a discrimination between a microbe and its product or role. Fix this table.

Foods and beverages

  • Lactobacillus / LAB -> curd (and lactic acid); Saccharomyces cerevisiae -> bread dough + ethanol; Propionibacterium sharmanii -> Swiss cheese (CO2 makes the large holes); Penicillium roqueforti -> Roquefort cheese (fungus-ripened).

Industrial acids and antibiotic

  • Aspergillus niger -> citric acid; Acetobacter aceti -> acetic acid; Clostridium butylicum -> butyric acid; Lactobacillus -> lactic acid; Penicillium notatum -> penicillin (Fleming).

Enzymes and bioactive molecules

  • Lipase -> detergents; Pectinase / protease -> clarify fruit juices; Streptokinase (from Streptococcus) -> clot buster; Cyclosporin A (from Trichoderma polysporum) -> immunosuppressant; Statins (from Monascus purpureus) -> lower blood cholesterol (by competitive inhibition).

Biocontrol, biofertiliser and biogas

  • Bacillus thuringiensis -> caterpillars; Trichoderma -> plant pathogens; Baculovirus (Nucleopolyhedrovirus) -> insects (narrow-spectrum); ladybird -> aphids; dragonfly -> mosquitoes.
  • Rhizobium -> symbiotic N-fixation (legume nodules); Azospirillum / Azotobacter -> free-living N-fixation; Glomus (mycorrhiza) -> phosphorus uptake; Anabaena / Nostoc / Oscillatoria (cyanobacteria) -> N-fixation.
  • Methanogens (Methanobacterium) -> methane / biogas.

Trap: the same genus can appear twice - Lactobacillus makes both curd and lactic acid; Trichoderma is both a biocontrol agent and the source of cyclosporin A (so it is NOT a household microbe).

Fine Distinctions and Traps

Cheeses and beverages

  • Swiss cheese = large holes from CO2 by Propionibacterium; Roquefort = ripened by the fungus Penicillium roqueforti.
  • Non-distilled = wine and beer; distilled = whisky, brandy, rum (higher alcohol).

Who can and cannot fix nitrogen

  • Nitrogen-fixers: Rhizobium, Azotobacter, Azospirillum (bacteria) and the cyanobacteria Anabaena, Nostoc, Oscillatoria.
  • NOT nitrogen-fixers: green algae such as Volvox and Chlorella (they are not even bacteria).
  • Symbiotic N-fixer = Rhizobium (needs a legume host); free-living N-fixers = Azotobacter, Azospirillum.
  • Mycorrhiza (Glomus) absorbs PHOSPHORUS, not nitrogen.

Role confusions

  • Biocontrol vs biofertiliser: Trichoderma, Bt and Baculovirus are biocontrol; Rhizobium, Glomus and cyanobacteria are biofertilisers. Do not mix them.
  • Streptokinase = clot buster (heart attack), NOT cholesterol; statins = lower cholesterol, NOT clots; cyclosporin A = immunosuppressant.

Sewage treatment

  • Primary = physical (filtration + sedimentation); secondary = biological (aeration -> flocs -> BOD falls).
  • The major part of the activated sludge -> anaerobic digester (makes biogas); a small part -> inoculum back into the aeration tank.
  • BOD measures organic matter: higher BOD = more polluted water.

Assertion-Reason watch-outs: Baculoviruses are species-specific and narrow-spectrum, which is exactly why they are desirable in IPM (R correctly explains A); statins work by competitively inhibiting the enzyme of cholesterol synthesis.