Microbial Ecology- Part I

1. Definition of Microbial ecology

2. Importance of microbial ecology

3. Structure of Microbial Communities in an Environment

4. Organisation of the Microbial Community in an Environment

Microbes have developed strategies which enable them to survive:




High reproduction rate allows survival

Low reproduction rates

High nutrients enables rapid growth to outcompete other cells

Low nutrients available ie nutrient limiting conditions.

Crowded conditions exist

Less crowded

Subject to extreme population fluctuations when nutrients are depleted

More permenant and stable members of the community

Ex: Cyanobacterial blooms due to PO4, Pseudomonas responds to increased carbon source

Ex: Spirilla and vibrios in marine environments, prostecate bacteria in oligotrophic lakes


5. Colonization & succession within microbial communities


6. Interactions within a single microbial population


7. Interactions between diverse microbial populations

 Intearction between two microbial populations can positively or negatively affect one or both populations; a neutral outcome is also possible.

(a) Synergism:


(b) Mutualism (Symbiosis):


 (c) Amensalism (Antagonism):



Produced by

Bactericidal against

Lactocin S

Lactobacillus sake

Gram-positive bacteria


Propionibacterium thoenii

Gram-negative bacteria


Lactobacillus plantarum

Inhibits endospore germination