Editing Gram stain (section)

=== Gram-variable and gram-indeterminate bacteria ===
{{anchor|Gram-variable and gram-indeterminate bacteria|Gram-indeterminate bacteria|reason=Former names of this section; may have incoming links.}}
Some bacteria, after staining with the Gram stain, yield a gram-variable pattern: a mix of pink and purple cells are seen.<ref name=":0" /><ref name="Beveridge_1990">{{cite journal |url= |first=Terry J. |last=Beveridge |title=Mechanism of Gram Variability in Select Bacteria |journal=Journal of Bacteriology |date=March 1990 |volume=172 |issue=3 |pages=1609–1620 |pmid=1689718 |pmc=208639 |doi=10.1128/jb.172.3.1609-1620.1990}}</ref> In cultures of ''Bacillus, Butyrivibrio'', and ''Clostridium'', a decrease in peptidoglycan thickness during growth coincides with an increase in the number of cells that stain gram-negative.<ref name="Beveridge_1990" /> In addition, in all bacteria stained using the Gram stain, the age of the culture may influence the results of the stain.<ref name="Beveridge_1990" />

Gram-indeterminate bacteria do not respond predictably to Gram staining and, therefore, cannot be determined as either gram-positive or gram-negative. Examples include many species of ''[[Mycobacterium]]'', including ''Mycobacterium bovis'', ''[[Mycobacterium leprae]]'' and ''[[Mycobacterium tuberculosis]]'', the latter two of which are the causative agents of leprosy and tuberculosis, respectively.<ref>{{cite book |last=Black |first=Jacquelyn |title=Microbiology: Principles and Exploration |edition=8th |date=2012 |publisher=John Wiley & Sons |isbn=978-0-470-54109-8 |page=68}}</ref><ref name="pmid19885935">{{cite book |last1=Reynolds |first1=J. |last2=Moyes |first2=R. B. |last3=Breakwell |first3=D. P. |title=Differential staining of bacteria: Acid fast stain |journal=[[Current Protocols#Titles|Current Protocols in Microbiology]] |date=2009 |chapter=Appendix 3 |volume=Appendix 3 |pages=H |doi=10.1002/9780471729259.mca03hs15 |pmid=19885935 |isbn=978-0471729259|s2cid=45685776 }}</ref> Bacteria of the genus ''[[Mycoplasma]]'' lack a [[cell wall]] around their [[cell membrane]]s,<ref name=Sherris>{{cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | pages=409–12 |edition = 4th | publisher = McGraw Hill | year = 2004 | isbn = 978-0-8385-8529-0}}</ref> which means they do not stain by Gram's method and are resistant to the antibiotics that target cell wall synthesis.<ref name="pmid23085510">{{cite journal |vauthors=Lee EH, Winter HL, van Dijl JM, Metzemaekers JD, Arends JP |title=Diagnosis and antimicrobial therapy of Mycoplasma hominis meningitis in adults |journal=International Journal of Medical Microbiology |volume=302 |issue=7–8 |pages=289–92 |date=December 2012 |pmid=23085510 |doi=10.1016/j.ijmm.2012.09.003 |url=}}</ref><ref name="pmid30003864">{{cite journal |vauthors=Gautier-Bouchardon AV |title=Antimicrobial Resistance in Mycoplasma spp |journal=Microbiology Spectrum |volume=6 |issue=4 |pages= 425–446|date=July 2018 |pmid=30003864 |doi=10.1128/microbiolspec.ARBA-0030-2018 |isbn=9781555819798 |s2cid=51616821 |url=|pmc=11633602 }}</ref>