The previous experiment demonstrated how different immunizing schedules shape the interaction between host and parasite. The image below depicts three states of a two-CA system: Isolation, encroachment and immunity. CA-2 immunity is manifested by two features: 1. CA-2 thrives and kills CA-1. We may wonder what happens to the system after eliminating the parasite? In the present experiment, both CA interact and I = { +, +}. CA-1 was then killed at rising times.
When CA-2 dies soon after CA-1 is killed it indicates,
that during their brief encounter CA-2 benefited from a vital substance
produced by CA-1 In 18% of
such encounters CA-2 developed an absolute
dependency on the CA-1 product. In the rest CA-2 may have also benefited, yet remained
independent and survived
CA-1 killing.
Each curve starts with the value of an isolated CA-2, marked
by an A, and ends with a
value observed in an independent CA-2 marked by a B. An
isolated (or virgin) CA-2 did not interact with CA-1. while
the independent CA-2 interacted
with CA-1 until its killing or its own
death at t = 62 (see the image above) and then became independent..
Cell count proceeds through three phases:
I Partial dependency on CA-1.
Apparently CA-1 secreted a trophic factor which made the CA-2 bigger. Since
after CA-1 killing the factor
is missing, CA-2 shrunk.
II Independence: CA-2 remains big even when CA-1 was killed.
III Mounting dependence: CA-2 size declines until becoming smaller than that of an isolated CA-2
(B)
Production follows a similar course, only health is different.
From the beginning CA-2 becomes healthier (more efficient). Later
its health declines and becomes lower than that of an isolated CA-2 (B). On
t = 62 the immunized CA-2 kills CA-1
( see upper image). Its on going health deterioration results from a factor produced by CA-1
which after its death is missing.
Below are two representative CA-1.
Symbiosis and Parasitism
The relationship
between the two CA involves
more than just a one way exploitation. The declining parameters
indicate that both CA benefit from this relationship. Parasite and symbiont
are not as distinct as is commonly viewed. Each host parasite relationship involves also symbiosis,
which explains how parasites turn into symbionts. By a gradual shift of
dependencies between them and their host. Lyn Margulies believes that the
symbiosis between unicellular organism promoted the transition from prokaryotes to eukariotes.
Two unicellular organisms intended to exploit each other, but established
a mutual relationship similar to that described here. In the end one was
engulfed by the other and became
its nucleus.