Margulis, Lynn WORLD OF MICROBIOLOGY AND IMMUNOLOGY364•
with the appropriate nutrients, explaining the increased per-
meability of many solutes. However, the true nature of the
NPP remains an enigma. Possible causes for the NPP include
1) the parasite activates native transporters, 2) proteins pro-
duced by the parasite cause structural defects, 3) plasmodium
inserts itself into the channel thus affecting it’s function, and
4) the parasite makes the membrane more ‘leaky’. The prop-
erties of the transporters and channels on a normal RBC differ
dramatically from that of a malaria-infected RBC.
Additionally, the lipid composition in terms of its fatty acid
pattern is significantly altered, possibly due to the nature in
which the parasite interacts with the membrane of the RBC.
The dynamics of the membranes, including how the fats that
makeup the membrane are deposited, are also altered. The
increase in transport of solutes is bidirectional and is a func-
tion of the developmental stage of the parasite. In other words,
the alterations in erythrocyte membrane are proportional to the
maturation of the parasite.See alsoParasitesMMargulis, Lynn ARGULIS, LYNN(1938- )
American biologistLynn Margulis is a theoretical biologist and professor of
botany at the University of Massachusetts at Amherst. Her
research on the evolutionary links between cells containing
nuclei (eukaryotes) and cells without nuclei (prokaryotes) led
her to formulate a symbiotic theory of evolutionthat was ini-
tially spurned in the scientific community but has become
more widely accepted.
Margulis, the eldest of four daughters, was born in
Chicago. Her father, Morris Alexander, was a lawyer who
owned a company that developed and marketed a long-lasting
thermoplastic material used to mark streets and highways. He
also served as an assistant state’s attorney for the state of
Illinois. Her mother, Leone, operated a travel agency. When
Margulis was fifteen, she completed her second year at Hyde
Park High School and was accepted into an early entrant pro-
gram at the University of Chicago.
Margulis was particularly inspired by her science
courses, in large part because reading assignments consisted
not of textbooks but of the original works of the world’s great
scientists. A course in natural science made an immediate
impression and would influence her life, raising questions that
she has pursued throughout her career: What is heredity? How
do genetic components influence the development of off-
spring? What are the common bonds between generations?
While at the University of Chicago she met Carl Sagan, then a
graduate student in physics. At the age of nineteen, she married
Sagan, received a B.A. in liberal arts, and moved to Madison,
Wisconsin, to pursue a joint master’s degree in zoology and
genetics at the University of Wisconsin under the guidance of
noted cell biologist Hans Ris. In 1960, Margulis and Sagan
moved to the University of California at Berkeley, where she
conducted genetic research for her doctoral dissertation.The marriage to Sagan ended before she received her
doctorate. She moved to Waltham, Massachusetts, with her
two sons, Dorion and Jeremy, to accept a position as lecturer
in the department of biology at Brandeis University. She was
awarded her Ph.D. in 1965. The following year, Margulis
became an adjunct assistant of biology at Boston University,
leaving 22 years later as full professor. In 1967, Margulis mar-
ried crystallographer Thomas N. Margulis. The couple had
two children before they divorced in 1980. Since 1988,
Margulis has been a distinguished university professor with
the Department of Botany at the University of Massachusetts
at Amherst.
Margulis’ interest in genetics and the development of
cells can be traced to her earliest days as a University of
Chicago undergraduate. She always questioned the commonly
accepted theories of genetics, but also challenged the tradi-
tionalists by presenting hypotheses that contradicted current
beliefs. Margulis has been called the most gifted theoretical
biologist of her generation by numerous colleagues. A profile
of Margulis by Jeanne McDermott in the Smithsonianquotes
Peter Raven, director of the Missouri Botanical Garden and a
MacArthur fellow: “Her mind keeps shooting off sparks.
Some critics say she’s off in left field. To me she’s one of the
most exciting, original thinkers in the whole field of biology.”
Although few know more about cellular biology, Margulis
considers herself a “microbial evolutionist,” mapping out a
field of study that doesn’t in fact exist.
As a graduate student, Margulis became interested in
cases of non-Mendelian inheritance, occurring when the
genetic make-up of a cell’s descendants cannot be traced
solely to the genes in a cell’s nucleus. For several years, she
concentrated her research on a search for genes in the cyto-
plasmof cells, the area outside of the cell’s nucleus. In the
early 1960s, Margulis presented evidence for the existence of
extranuclear genes. She and other researchers had found DNA
in the cytoplasm of plant cells, indicating that heredity in
higher organisms is not solely determined by genetic informa-
tion carried in the cell nucleus. Her continued work in this
field led her to formulate the serial endosymbiotic theory, or
SET, which offered a new approach to evolution as well as an
account of the origin of cells with nuclei.
Prokaryotes—bacteria and blue-green algaenow com-
monly referred to as cyanobacteria—are single-celled organ-
isms that carry genetic material in the cytoplasm. Margulis
proposes that eukaryotes (cells with nuclei) evolved when dif-
ferent kinds of prokaryotes formed symbiotic systems to
enhance their chances for survival. The first such symbiotic
fusion would have taken place between fermenting bacteria
and oxygen-using bacteria. All cells with nuclei, Margulis con-
tends, are derived from bacteria that formed symbiotic rela-
tionships with other primordial bacteria some two billion years
ago. It has now become widely accepted that mitochondria—
those components of eukaryotic cells that process oxygen—are
remnants of oxygen-using bacteria. Margulis’ hypothesis that
cell hairs, found in a vast array of eukaryotic cells, descend
from another group of primordial bacteria much like the mod-
ern spirochaete still encounters resistance, however.womi_M 5/7/03 7:52 AM Page 364