AN INTRODUCTION TO BACTERIA

 BACTERIA

·       Prokaryotic in nature.

·       Christian Gottfried Ehrenberg introduced the word "bacterium" in 1828.

·       Measured in micrometer (µm)

·       Unicellular in nature.

·       Previously, Thiomargarita namibiensis was considered as Largest bacteria.

ü  Gram negative cocci.

ü  Alpha Proteobacteria.

ü  Chemolithotrophs.

ü  Found in the ocean sediments of the coast of Namibia in 1999.

ü  Large enough to be visible to the naked eye, attaining a size of 0.1– 0.3 mm or 100 to 300 µm in diameter.

·       Recently, the world's largest bacterium has been discovered amongst the Mangroves of the Caribbean island of Guadeloupe. Measuring over a centimetre long, Thiomargarita magnifica is over 5000 times bigger than the average microbe.

·       Longest bacteria - Epulopiscium fishelsoni

ü  Gram Positive Rods.

ü  Discovered in the Gut of Surgeon fish.

ü  Large enough to be seen with the naked eye at 600 µm. Million times larger than Escherichia coli and Bacillus sp.

·       Smallest bacteria – Mycoplasma genitalium

ü  Lives in the primate bladder, waste disposal organs, genital, and respiratory tracts.

ü   Measures about 200 nm – 300 nm in dm.

·       Reproduction – Asexual and Binary fission.

·  Cell wall is made up of peptidoglycan but some bacteria like Mycoplasma sp. lacks cell wall.                             

·       Based on the Guanine and Cytosine (G+C) content in DNA, bacteria are classified in 3 categories. They are: (i) Actinobacteria (previously called as Actinomycetes) (high G+C content) (Frankia sp. and Streptomyces sp.), (ii) Firmicutes (low G+C content) (Megasphaera sp., Pectinatus sp., Selenomonas sp. and Zymophilus sp.) and (iii) Tenericutes (no cell wall) (E.g. Mycoplasma sp., Spiroplasma sp., Ureaplasma sp. and Phytoplasma sp.)  

·       Locomotion – Flagella. Some are motile and few are non – motile.

· Cyanobacteria, also known as Cyanophyta is a phylum of bacteria that obtain energy through photosynthesis are the only photosynthetic prokaryotes able to produce oxygen. The name "cyanobacteria" comes from the color of the bacteria (blue). Cyanobacteria (which are prokaryotes) used to be called "Blue green algae". They have been renamed 'Cyanobacteria' in order to avoid the term "algae", which in modern usage is restricted to eukaryotes.

·       Study of Bacteria – Bacteriology.

·       Father of Bacteriology – Robert Koch.