Environmental Microbiology of Aquatic and Waste Systems

4.1 Taxonomy of Microorganisms in Aquatic Environments 49

Aquifex

Thermotoga

Flavobacteria

Cyanobacteria

Purple bacteria

Gram +ve

bacteria

Greennon-sulphur

bacteria

Pyrodictium

Thermoproteus

Thermo-

coccus

Methanococcus

Methanobacterium

Extreme

thermophiles

Thermo-

plasma

Diplomonads

Microsporidia

Trichomonads

Flagellates

Entamoeba

Slime

fungi

Plants

Fungi

Animals

Eucarya

Bacteria

Archaea

Fig. 4.1 Three domains of living things based on Woese’s work (Modified from Ciccarelli et al. 2006 )

Table 4.1 Summary of differences among the three domains of living things (Modified from Madigan and Martinko 2006 )

S. No. Characteristic Bacteria Archae Eukarya

1. Prokaryotic cell structure + + −


2. DNA present in closed circular form + + −


3. Histone proteins presenta − + +


4. Nuclear membrane − − +


5. Muramic acid in cell wall + − −


6. Membrane lipids: Fatty acids or branched hydrocarbons Fatty acids Branched
   hydrocarbons

Fatty acids

Unbranched fatty acid chains attached to glycerol by ester linkages + − +

7. Ribosome size 70 S 70 S 80 S


8. Initiator t­RNA Formyl­methionine Methionine Methionine


9. Introns in most genesb − − +


10. Operonsc + + −


11. Plasmids + + Rare


12. Ribosome sensitive to diphtheria toxin − + +


13. Sensitivity to streptomycin, chloramphenicol, and kanamycin + − −
    Physiological/special structures


14. Methanogenesis + + −


15. Denitrification + + −


16. Nitrogen fixation + + −


17. Chlorophyll­based photosynthesis + – + (Plants)


18. Gas vesicles + + −


19. Chemolithotrophy + + −


20. Storage granules of poly­b­hydroxyalkanoates + + −


21. Growth above 80°C + + −


22. Growth above 100°C − + −
    aHistone proteins are present in eukaryotic chromosomes; histones and DNA give structure to chromosomes in eukaryotes; proteins
    in archeae chromosomes are different
    bNoncoding sequences within genes
    cOperons: Typically present in prokaryotes, these are clusters of genes controlled by a single operator
    dTATA box (also called Hogness Box): an AT­rich region of the DNA with the sequence TATAT/AAT/A located before the initiation site
    eTranscription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription