Borrelia burgdorferi, the cause of Lyme Disease
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"Veni, vidi, vici" - Julius Caesar "I came, I saw, I conquered"


Once in a host, B. burgdorferi reproduces asexually through mitosis to make a colony.  The species has not yet been found naturally outside of a host, and therefore it needs a host in order to reproduce.  It has been known to spread into the blood, cerebrospinal fluid, heart, retina, brain, muscles, bone, spleen, liver, and brain (Schnarr, S., Franz, J., Krause, A., & Zeidler, H., 2006). While B. burgdorferi reproduces asexually through binary fission like most other bacterium, they also have an unique variations of reproduction.  Sometimes a cyst forms in which young  B. burgdorferi form and are later released.  Also, buds may form on the lengthwise section of  B. burgdorferi.  These buds can eventually turn into cysts that contain growing  B. burgdorferi and burst to release the bacterium.  Additionally,  B. burgdorferi is unique in its ability to reproduce essentially wherever and whenever it needs to while protecting itself from its hosts' immune system (Karlen, A., 2000). 

The lifecycle of  Borrelia burgdorferi revolves closely around the lifecycle of its primary host, Ixoidid ticks.  In early summer, when a tick larva hatches and attaches to a host, the larva can become infected with Borrelia burgdorferi.  Generally, the ticks host will have been previously infected with B. burgdorferi at some point in its lifetime from a different tick nymph and therefore, continues to carry  B. burgdorferi.  This host, a mouse/small mammal for example, will pass the spirochetes species on to many ticks throughout its lifetime.  Therefore, the tick is B. burgdorferi's vector (animal that acts as a carrier and transmitter of a pathogenic organism), while the mouse/small mammal is  B. burgdorferi's reservoir (a holding area for the pathogenic species) (Karlen, A., 2000). 

Once the tick bites into its host,  B. burgdorferi needs to quickly adapt to a new environment as it enters through the blood rushing into the tick's mouth and continues to flow into the tick's gut.   Because of the tenacity and toughness of B. burgdorferi, it adjusts to the colder temperature and different immune system.  It also changes its nourishment source from that of the mammalian blood to the hemolymph that flows through the tick.  Once in the tick's gut, B. burgdorferi clings to the lining of the gut through its surface proteins (explained in the Adaptation section) and grows colonies in the lining of the gut (Once a colony is developed, "B. burgdorferi penetrates the gut wall and multiplies in spaced between cells" (Karlen, A., 2000).  It's ability to penetrate the gut is directly correlated to B. burgdorferi's spiral shape and unique flagella movement allowing it to invade tissues and cells through a cork-screw motion.

B. burgdorferi remains in this state in the gut until the tick feeds again.  B. burgdorferi will then be reactivated and enter the ticks hemolymph system which carries it to the salivary glands.  It is in the salivary glands were B. burgdorferi can be transmitted through saliva to a new host. However, the larva tick cannot transmit B. burgdorferi to a new host; therefore, after growing into a nymph it must detach from its host (the mouse/small mammal) and survive the winter (nymph dormant stage of lifecycle). The following summer the tick will look for its second host. picture of how to safelly remove ticks

When the tick bites into this new host, B. burgdorferi again changes its environment as it infects the host wound.  The saliva of the tick surrounds B. burgdorferi and provides help by altering the hosts immune system at the site of the wound.  The heat shock proteins (explained in the Adaptation section) assist this bacterium in surviving the warmer host environment.  The Osps (explained in the Adaptation section) also help B. burgdorferi establish a colony within the host.  Once again due to B. burgdorferi's motile abilities, it can penetrate the tissue of this secondary host and infect the host allowing the host to become a reservoir to infect other ticks.  When the nymph tick is done feeding, it drops off its host, becomes an adult, and survives the winter.  The next spring the adult tick can reproduce and once again will attach to another host (usually a larger mammal) to continue the B. burgdorferi infectious cycle (Karlen, A., 2000).