What You Didn't Know About Jan­thi­nobac­terium

by Jenna Ta­bor-God­win, Rhona Stu­art, Rosa I. León Za­yas, and Chi­tra Ra­jaku­beran*

Some bugs are ex­cit­ing but it takes them a while to be­come well known. The rod-shaped, Gram-neg­a­tive Jan­thinobacterium lividum falls in this cat­e­gory. But re­cent dis­cov­er­ies about its phys­i­ol­ogy, ecol­ogy, and med­i­cine high­light its im­por­tance. J. lividum is com­monly found in soil and bod­ies of wa­ter, but can also turn up in spoiled milk and, on rare oc­ca­sions, can cause sep­ticemia in hu­mans. Lest you think that its name hon­ors some­one called Jan­thin, jan­thi­nus is Latin for vi­o­let-col­ored. (It used to be called Chro­mobac­terium.) It is aer­o­bic and can be cul­tured. Colonies are pur­plish-black due to its wa­ter-in­sol­u­ble pig­ment called vi­o­la­cein. This pig­ment is pref­er­en­tially pro­duced when glyc­erol is the car­bon source. There is a cor­re­la­tion be­tween vi­o­la­cein pro­duc­tion, biofilm for­ma­tion, and greater sur­vival, sug­gest­ing that it may play a role in re­sponse to en­vi­ron­men­tal stress.

an­thi­nobac­terium cul­tured on NB agar. Source

While vi­o­la­cein ben­e­fits the host di­rectly, it is also known to be toxic against bac­te­ria, viruses, pro­tozoa, and fungi. A re­cent study showed that J. lividum also pro­duces in­dole-3-car­box­alde­hyde, and that this plays a role in a pos­si­ble mu­tu­al­is­tic re­la­tion­ship with the red-backed sala­man­der Pletho­don cinereus. These sala­man­ders are of­ten in­fected with the chytrid fun­gus Batrachochy­trium den­dro­ba­tidis, one of the main pathogens im­pli­cated in the near ex­tinc­tion of cer­tain am­phibians. B. den­dro­ba­tidis in­fects the skin of am­phib­ians and causes a dis­ease known as chytri­diomycosis. Am­phib­ian species that carry higher amounts of J. lividum can with­stand this devas­tating in­fec­tion be­cause the anti-fun­gal com­pounds pro­duced by the bac­te­ria are lethal to B. den­dro­ba­tidis. Ex­ploit­ing the bi­o­log­i­cal prop­er­ties of J. lividum may help to pro­vide anti-fun­gal re­sis­tance to the dwin­dling am­phib­ian pop­u­la­tion.
 

An adult red-backed sala­man­der, Pletho­don cinereus. Source

In ad­di­tion to its anti-fun­gal prod­uct, three an­tibi­otics pro­duced by J. lividum act against both Gram-neg­a­tive and Gram-pos­i­tive bac­te­ria. (They're be­ing patented.) Be­sides mak­ing its own an­tibi­otics, J. lividum also has the ca­pac­ity to re­sist oth­ers. It was re­cently found to pos­sess a di­ver­gent, in­ducible, chro­mo­so­ma­lly-en­coded met­allo-β-lac­ta­mase (MBL) called THIN‑B, which, when cloned into Es­cherichia coli, con­ferred greater re­sis­tance to β‑lactam an­tibi­otics. MBLs have be­come in­creas­ingly well known be­cause var­i­ous pathogens have be­come an­tibi­otic-re­sis­tant due to mo­bile MBLs. While none of these mo­bile MBLs have been de­fin­i­tively traced back to an en­vi­ron­men­tal, non-patho­­genic strain, it is con­sid­ered likely that such strains are serv­ing as a reser­voir. The mo­bile MBLs are most com­monly en­coded by gene cas­settes in class 1 in­te­grons and are be­com­ing wide­spread in Acine­to­bac­ter and Pseudomonas, two bugs well known for caus­ing hos­pi­tal-ac­quired in­fec­tions. The func­tion of these genes in the en­vi­ron­men­tal strains is cur­rently a mys­tery. If the only func­tion of MBLs is to pro­vide re­sis­tance to β‑lactams, why are they so wide­spread in en­vi­ron­ments where β‑lactams are not com­mon? In what seems to be a puz­zling anom­aly, J. lividum is unique among β‑proteobacteria in mak­ing an MBL.

J. lividum has many fas­ci­nat­ing at­trib­utes that will surely be stud­ied more in years to come. With only 43 PubMed hits, there is still much to learn about J. lividum. If you didn't know much about it be­fore, well, now you know a bit more.

*Jenna, Rhona, Rosa, and Chi­tra were stu­dents in the Uni­ver­sity of Cal­i­for­nia at San Diego/San Diego State Uni­ver­sity In­te­gra­tive Mi­cro­bi­ol­ogy grad­u­ate course dur­ing the 2009 win­ter quar­ter.