Michael Eisenbach

Michael Eisenbach (Hebrew: מיכאל אייזנבך) is an Israeli biochemist who specializes in the navigation mechanisms of bacterial and sperm cells.^[1] He is a professor emeritus at the Weizmann Institute of Science, Department of Biomolecular Sciences, Rehovot, Israel.^[2] He discovered that sperm cells (spermatozoa) of mammals are actively guided to the egg.^[3] This opened the research field of mammalian sperm navigation (also termed sperm guidance). ^[4]

Eisenbach was born in Tel Aviv, Israel on 10 April 1945. His parents, Menachem (Mendel; 1906–1976) and Haya (Helena Leibler; 1910–1993) Eisenbach, were born in Poland and immigrated to Israel at the end of 1934. Most of their family members remained in Poland and were exterminated in the Holocaust.

Eisenbach attended Tel Aviv University. He received his B.Sc. in chemistry (1969), M.Sc. (with distinction, 1971) and Ph.D. in biochemistry (1975). For his M.Sc., he studied, under the supervision of Chanoch Carmeli, the photosynthetic electron transport chain in chloroplasts.^[5] For his Ph.D., he studied, under the supervision of Menachem (Hemi) Gutman, the respiratory electron transport chain in mitochondria.^[6]

He then moved to the Weizmann Institute of Science for postdoctoral study under the supervision of S. Roy Caplan, where he investigated the proton pump activity of bacteriorhodopsin in the purple membrane of archaea (1975–1978).^[7]

He did a second postdoctoral fellowship in Madison, Wisconsin, USA where he studied bacterial chemotaxis under the supervision of Julius Adler (1978–1980).^[2]

In 1980, Eisenbach returned to the Weizmann Institute as a senior scientist (equivalent to assistant professor) and established his own research group as an independent investigator. Four years later he was promoted to associate professor with tenure, and in 1995 to professor. In 2015, he became a professor emeritus.^[2]

Eisenbach has held academic and leadership positions throughout his career, particularly within the Weizmann Institute of Science and in various national and international scientific organizations.^[8]

In the early 1990s, Eisenbach pioneered the study of mammalian sperm navigation, challenging the prevailing belief that such navigation was unnecessary due to the high number of spermatozoa in the female reproductive tract.^[9]

Eisenbach’s group first showed that human spermatozoa accumulate in diluted follicular fluid, correlating with the fertilization potential of the corresponding egg.^[10][11] Research on Bacterial Chemotaxis  Prior to and alongside his work on sperm navigation, Eisenbach conducted extensive research into the molecular mechanisms of chemotaxis in bacteria, particularly Escherichia coli and Salmonella. These organisms served as model systems for studying behavior at the molecular level. His group made significant contributions to understanding how bacteria regulate flagellar rotation in response to chemical gradients.^[12]

Key findings include:

• The bacterial flagellar motor has a default rotation direction, which is reversed upon binding of the signal protein CheY to the switch complex.^[13][14]

• Eisenbach’s website
• Michael Eisenbach publications indexed by Google Scholar