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#bacterial phylum

2 public questions tagged with this topic.

Microbial Classification

Which phylum includes Mycobacterium tuberculosis?

Mycobacterium tuberculosis belongs to phylum Actinobacteria, also called Actinomycetota, defined as high G+C Gram-positive bacteria typically ranging 60 to 75 mol percent guanine-cytosine content. Members exhibit complex filamentous growth, mycolic acid-containing cell envelope conferring acid-fastness, slow growth rates, and resistance to desiccation and disinfectants. Actinobacterial 16S rRNA signatures and genome GC content cluster Mycobacterium with Streptomyces, Corynebacterium, and Nocardia. This lineage possesses unique arabinogalactan peptidoglycan and lipoarabinomannan, distinguishing it clearly from low G+C Firmicutes, Proteobacteria, and Bacteroidetes in modern bacterial systematics and clinical diagnostics.

Ref: Campbell Biology 12th ed., Chapter 27 Actinobacteria high GC Mycobacterium; Tortora Microbiology Chapter 11 Actinomycetes acid-fastness

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Microbial Classification

Firmicutes are characterized by

Firmicutes, now reclassified as Bacillota, represent low G+C monoderm bacteria characterized by an exceptionally thick multilayered peptidoglycan network crosslinked with peptide interbridges and anionic teichoic acids. This robust wall retains crystal violet-iodine complex during Gram staining, conferring positive reaction and protection against osmotic stress. It serves as target for lysozyme and beta-lactams. Members include Bacillus, Clostridium, Staphylococcus, and Lactobacillus, exhibiting endospore formation in some genera. Despite occasional Gram-negative staining variants, thick peptidoglycan remains defining diagnostic feature separating them from Gracilicutes.

Ref: Bergey's Manual Systematic Bacteriology Volume 3 Firmicutes thick peptidoglycan; Prescott Microbiology 10th ed., Chapter 15 Gram-positive bacteria

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