Filamentation

A Bacillus cereus cell that has undergone filamentation following antibacterial treatment (upper electron micrograph; top right) and regularly sized cells of untreated B. cereus (lower electron micrograph)

Filamentation is the anomalous growth of certain bacteria, such as Escherichia coli, in which cells continue to elongate but do not divide (no septa formation).[1][2] The cells that result from elongation without division have multiple chromosomal copies.[1]

In the absence of antibiotics or other stressors, filamentation occurs at a low frequency in bacterial populations (4–8% short filaments and 0–5% long filaments in 1- to 8-hour cultures).[3] The increased cell length can protect bacteria from protozoan predation and neutrophil phagocytosis by making ingestion of cells more difficult.[1][3][4][5] Filamentation is also thought to protect bacteria from antibiotics, and is associated with other aspects of bacterial virulence such as biofilm formation.[6][7]

The number and length of filaments within a bacterial population increases when the bacteria are exposed to different physical, chemical and biological agents (e.g. UV light, DNA synthesis-inhibiting antibiotics, bacteriophages).[3][8] This is termed conditional filamentation.[2] Some of the key genes involved in filamentation in E. coli include sulA, minCD and damX.[9][10]

  1. ^ a b c Jaimes-Lizcano YA, Hunn DD, Papadopoulos KD (April 2014). "Filamentous Escherichia coli cells swimming in tapered microcapillaries". Research in Microbiology. 165 (3): 166–74. doi:10.1016/j.resmic.2014.01.007. PMID 24566556.
  2. ^ a b Karasz DC, Weaver AI, Buckley DH, Wilhelm RC (January 2022). "Conditional filamentation as an adaptive trait of bacteria and its ecological significance in soils". Environmental Microbiology. 24 (1): 1–17. doi:10.1111/1462-2920.15871. OSTI 1863903. PMID 34929753. S2CID 245412965.
  3. ^ a b c Cushnie TP, O'Driscoll NH, Lamb AJ (December 2016). "Morphological and ultrastructural changes in bacterial cells as an indicator of antibacterial mechanism of action". Cellular and Molecular Life Sciences. 73 (23): 4471–4492. doi:10.1007/s00018-016-2302-2. hdl:10059/2129. PMID 27392605. S2CID 2065821.
  4. ^ Hahn MW, Höfle MG (May 1998). "Grazing pressure by a bacterivorous flagellate reverses the relative abundance of Comamonas acidovorans PX54 and Vibrio strain CB5 in chemostat cocultures". Applied and Environmental Microbiology. 64 (5): 1910–8. Bibcode:1998ApEnM..64.1910H. doi:10.1128/AEM.64.5.1910-1918.1998. PMC 106250. PMID 9572971.
  5. ^ Hahn MW, Moore ER, Höfle MG (January 1999). "Bacterial filament formation, a defense mechanism against flagellate grazing, is growth rate controlled in bacteria of different phyla". Applied and Environmental Microbiology. 65 (1): 25–35. Bibcode:1999ApEnM..65...25H. doi:10.1128/AEM.65.1.25-35.1999. PMC 90978. PMID 9872755.
  6. ^ Justice SS, Hunstad DA, Cegelski L, Hultgren SJ (February 2008). "Morphological plasticity as a bacterial survival strategy". Nature Reviews. Microbiology. 6 (2): 162–8. doi:10.1038/nrmicro1820. PMID 18157153. S2CID 7247384.
  7. ^ Fuchs BB, Eby J, Nobile CJ, El Khoury JB, Mitchell AP, Mylonakis E (June 2010). "Role of filamentation in Galleria mellonella killing by Candida albicans". Microbes and Infection. 12 (6): 488–96. doi:10.1016/j.micinf.2010.03.001. PMC 288367. PMID 20223293.
  8. ^ Ragunathan PT, Vanderpool CK (December 2019). "Cryptic-Prophage-Encoded Small Protein DicB Protects Escherichia coli from Phage Infection by Inhibiting Inner Membrane Receptor Proteins". Journal of Bacteriology. 201 (23). doi:10.1128/JB.00475-19. PMC 6832061. PMID 31527115.
  9. ^ Bi E, Lutkenhaus J (February 1993). "Cell division inhibitors SulA and MinCD prevent formation of the FtsZ ring". Journal of Bacteriology. 175 (4): 1118–1125. doi:10.1128/jb.175.4.1118-1125.1993. PMC 193028. PMID 8432706.
  10. ^ Khandige S, Asferg CA, Rasmussen KJ, Larsen MJ, Overgaard M, Andersen TE, Møller-Jensen J (August 2016). Justice S, Hultgren SJ (eds.). "DamX Controls Reversible Cell Morphology Switching in Uropathogenic Escherichia coli". mBio. 7 (4). doi:10.1128/mBio.00642-16. PMC 4981707. PMID 27486187.