GATE Environmental Engineering Environmental Microbiology Syllabus

Environmental Microbiology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Environmental Microbiology in GATE Environmental Engineering, not a summary of it.

1. 1

   Prokaryotic and Eukaryotic Microorganisms

   8 topics

   • Characteristics of Microorganisms
   • Classification of Microorganisms
   • Microbial Diversity
   • Plant-Microbe Interactions
   • Soil-Microbe Interactions
   • Role of Microorganisms in Wastewater Treatment
   • Role of Microorganisms in Bioremediation
   • Role of Microorganisms in Biogeochemical Cycling
2. 2

   Cell Chemistry and Cell Biology

   16 topics

   • Structure of Proteins
   • Structure of Nucleic Acid (DNA & RNA)
   • Structure of Lipids
   • Structure of Polysaccharides
   • Bonds in Biomolecules
   • Stereoisomerism in Biomolecules
   • Structure of Cell
   • Structure and Function of Cytoplasmic Membrane
   • Structure and Function of Cell Wall
   • Structure and Function of Outer Membrane
   • Structure and Function of Glycocalyx
   • Structure of Chromosomes
   • Structure of Endospores
   • Storage Products in Microbes
   • Structure and Function of Mitochondria
   • Structure and Function of Chloroplasts
3. 3

   Microbial Metabolism

   9 topics

   • Anabolism and Catabolism
   • Phosphorylation
   • Glycolysis
   • TCA Cycle
   • Electron Transport Chain
   • Fermentation
   • Anaerobic Respiration
   • Energy Balances in Microbial Metabolism
   • Enzymes and Enzyme Kinetics
4. 4

   Growth and Control of Microorganisms

   8 topics

   • Bacterial Nutrition and Growth
   • Specific Growth Rate and Doubling Time
   • Monod’s Model
   • Types of Culture Media
   • Batch and Continuous Culture
   • Effects of Environmental Factors on Growth
   • Control of Microbes using Physical Methods
   • Control of Microbes using Chemical Methods
5. 5

   Microbiology and Health

   4 topics

   • Pathogens and Modes of Transmission
   • Indicator Organisms
   • Quantification of Coliforms using MPN Techniques
   • Quantification of Coliforms using Membrane Filtration Techniques

Environmental Microbiology flashcards for GATE Environmental Engineering

23 of 49 cards from the Environmental Microbiology deck — real questions with worked answers.

1. What are the defining characteristics of microorganisms?

   Microorganisms are microscopic organisms (typically $<0.1\,\text{mm}$, requiring a microscope to see) that include bacteria, archaea, fungi, protozoa, algae, and viruses. They are ubiquitous, metabolically diverse, reproduce rapidly, and have a high surface-area-to-volume ratio enabling fast nutrient exchange.

2. What is the typical size range of bacteria, and how does it compare to viruses?

   Bacteria are typically $0.5$–$5\,\mu\text{m}$. Viruses are much smaller, typically $20$–$300\,\text{nm}$ ($0.02$–$0.3\,\mu\text{m}$), making them about $10$–$100$ times smaller than bacteria.

3. What distinguishes prokaryotic cells from eukaryotic cells?

   Prokaryotes lack a membrane-bound nucleus and membrane-bound organelles; their DNA is a single circular chromosome in the nucleoid. Eukaryotes have a true membrane-bound nucleus, linear chromosomes, and organelles (mitochondria, ER, Golgi). Prokaryotic ribosomes are 70S; eukaryotic are 80S.

4. Define generation (doubling) time and give the exponential growth equation for a bacterial population.

   Generation time is the time required for a population to double. Growth follows $N = N_0 \cdot 2^{n}$, where $n$ is the number of generations. With $t$ the time and $t_d$ the doubling time, $n = \frac{t}{t_d}$, so $N = N_0 \cdot 2^{t/t_d}$.

5. What are the three domains in the modern (Woese) classification of life, and on what molecule is it based?

   The three domains are Bacteria, Archaea, and Eukarya. The classification is based on comparison of small-subunit (16S/18S) ribosomal RNA gene sequences.

6. How are microorganisms classified by their carbon and energy sources?

   By energy: phototrophs (light) vs chemotrophs (chemical). By carbon: autotrophs ($\ce{CO2}$) vs heterotrophs (organic carbon). Combined: photoautotroph, photoheterotroph, chemoautotroph (chemolithotroph), and chemoheterotroph (chemoorganotroph).

7. Classify microorganisms by their relationship to oxygen.

   Obligate aerobes (require $\ce{O2}$), obligate anaerobes ($\ce{O2}$ is toxic), facultative anaerobes (grow with or without $\ce{O2}$, prefer it), microaerophiles (require low $\ce{O2}$), and aerotolerant anaerobes (ignore $\ce{O2}$, ferment).

8. How are microorganisms classified by optimal growth temperature?

   Psychrophiles (optimum $<15\,^{\circ}\text{C}$), mesophiles ($20$–$45\,^{\circ}\text{C}$), thermophiles ($45$–$80\,^{\circ}\text{C}$), and hyperthermophiles ($>80\,^{\circ}\text{C}$). Most pathogens and wastewater organisms are mesophiles.

9. What is microbial diversity and why is it important in environmental systems?

   Microbial diversity is the variety of microbial species, genes, and metabolic functions in a habitat. It underpins ecosystem stability, nutrient cycling, biodegradation, and resilience to perturbation. Functional redundancy among diverse taxa maintains processes when some species are lost.

10. Name common indices used to quantify microbial species diversity.

    Shannon-Wiener index $H = -\sum_{i=1}^{S} p_i \ln p_i$ and Simpson's index $D = \sum p_i^{2}$ (dominance), with diversity expressed as $1-D$ or $\frac{1}{D}$, where $p_i$ is the proportional abundance of species $i$ and $S$ is species richness.

11. What is the difference between mutualism, commensalism, and parasitism in plant-microbe interactions?

    Mutualism: both partners benefit (e.g., rhizobia-legume). Commensalism: one benefits, the other unaffected. Parasitism: microbe benefits at the host's expense (plant pathogens). Amensalism: one is harmed, the other unaffected.

12. Describe the rhizobia-legume symbiosis and its significance.

    Rhizobia (e.g., $\textit{Rhizobium}$) infect legume root hairs, forming root nodules where they fix atmospheric $\ce{N2}$ into $\ce{NH3}$ via nitrogenase in exchange for plant photosynthate. This biological nitrogen fixation enriches soil nitrogen without synthetic fertilizer.

13. What are mycorrhizae and what benefit do they provide to plants?

    Mycorrhizae are symbiotic associations between fungi and plant roots. The fungal hyphae extend the root's absorptive surface, improving uptake of water and nutrients (especially phosphorus), in exchange for plant sugars. Types include arbuscular (endo-) and ectomycorrhizae.

14. What is the rhizosphere and why is microbial activity elevated there?

    The rhizosphere is the narrow zone of soil surrounding and influenced by plant roots. Microbial activity is high because roots exude sugars, amino acids, and organic acids (rhizodeposition) that serve as carbon and energy sources for microbes.

15. Why is soil considered the most diverse microbial habitat, and how do microbes affect soil structure?

    Soil offers diverse microhabitats, surfaces, and nutrient gradients, supporting up to $10^{9}$ cells per gram. Microbes (and fungal hyphae) secrete extracellular polymeric substances that bind particles into aggregates, improving soil structure, aeration, and water retention.

16. What roles do soil microorganisms play in nutrient availability?

    They decompose organic matter (mineralization), fix nitrogen, solubilize phosphorus and potassium, nitrify and denitrify, and immobilize nutrients. These processes regulate the supply of plant-available $\ce{N}$, $\ce{P}$, $\ce{S}$, and micronutrients.

17. Which microbial groups dominate aerobic biological wastewater treatment, and what is their function?

    Heterotrophic bacteria (e.g., $\textit{Pseudomonas}$, $\textit{Zoogloea}$) oxidize organic matter (BOD), while autotrophic nitrifiers ($\textit{Nitrosomonas}$, $\textit{Nitrobacter}$) oxidize ammonia. Protozoa and rotifers graze dispersed bacteria, polishing the effluent.

18. Write the overall stoichiometry of microbial aerobic oxidation of organic matter using glucose.

    $$\ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O}$$ Microbes use part of the substrate for energy (catabolism) and part for new cell synthesis (anabolism).

19. What is the two-step nitrification process and which organisms catalyze each step?

    Step 1 ($\textit{Nitrosomonas}$): $\ce{NH4^+ + 1.5 O2 -> NO2^- + 2H^+ + H2O}$. Step 2 ($\textit{Nitrobacter}$): $\ce{NO2^- + 0.5 O2 -> NO3^-}$. Both are aerobic chemoautotrophs.

20. What is denitrification and under what conditions does it occur?

    Denitrification is the anoxic microbial reduction of nitrate to nitrogen gas: $\ce{NO3^- -> NO2^- -> NO -> N2O -> N2}$. It occurs under anoxic (no $\ce{O2}$) conditions with available organic carbon, removing nitrogen from wastewater as $\ce{N2}$ gas.

21. What are the main phases and microbial groups in anaerobic digestion?

    Hydrolysis (breaks polymers to monomers), acidogenesis (to VFAs), acetogenesis (to acetate, $\ce{H2}$, $\ce{CO2}$), and methanogenesis (to $\ce{CH4}$). Methanogens are archaea; the final step yields biogas: $\ce{CH4 + CO2}$.

22. What is bioremediation and what are its two broad categories?

    Bioremediation is the use of microorganisms (or plants) to degrade, transform, or immobilize environmental contaminants. Categories: in situ (treated in place, e.g., bioventing, biosparging) and ex situ (excavated/pumped and treated, e.g., landfarming, bioreactors).

23. Distinguish biostimulation from bioaugmentation in bioremediation.

    Biostimulation adds nutrients (N, P), electron acceptors, or oxygen to enhance the activity of indigenous microbes. Bioaugmentation introduces specialized exogenous microbial strains capable of degrading the target contaminant.

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