Michael Eisenbach

Eisenbach started learning to play the clarinet at the age of 70. In 2021, he became a member of the Maskit Clarinet Choir.

In 2004 a startup company, Repromed, was established with the aim of using thermotaxis to increase the success rate of artificial insemination. The company did not succeed, but a few years later, the concept was proven sound when a former postdoc of Eisenbach, Serafín Pérez-Cerezales, succeeded in demonstrating it.

In the middle of his scientific career, Eisenbach initiated the research field of mammalian sperm navigation. This was in the early 1990s, when the prevailing consensus was that there is no need for sperm navigation in mammals. This idea was based on the very large number of spermatozoa ejaculated into the limited space of the female genital tract. However, the prevailing theory did not take into account that the number of spermatozoa that actually succeed in entering the Fallopian tube is very small. With this background, Eisenbach’s group first found that human spermatozoa accumulate in diluted follicular fluid and that there is a remarkably strong correlation between the ability of follicular fluid from a particular follicle to cause sperm accumulation and the ability of the egg obtained from the same follicle to be fertilized. He then provided the first evidence that this sperm accumulation is the result of chemotaxis, accompanied by chemokinesis, and defined criteria for distinguishing chemotaxis from other processes that might cause sperm accumulation. His group further discovered that only a small fraction of the spermatozoa (~10% in humans) are chemotactically responsive and that the responsive spermatozoa are the capacitated ones (spermatozoa that have reached a maturation stage at which they can penetrate the egg and fertilize it). Whereas the capacitated state had generally been thought of as static, Eisenbach’s group found that the capacitated state is temporary (with a lifespan of 50–240 min for human spermatozoa in vitro), that there is a continuous process of replacement of capacitated spermatozoa within the sperm population, and that cells are phagocytized by macrophages once they lose their capacitation. He hypothesized, and then provided indirect evidence, that the physiological role of this continuous replacement of capacitated spermatozoa in humans is to prolong the availability of these spermatozoa to the egg during the relatively short time window when it resides in the fertilization site. His group then provided the first direct evidence that, subsequent to ovulation (i.e., outside the follicle), both the mature egg and its surrounding cumulus cells secrete chemoattractants and that progesterone is the main chemoattractant secreted from human cumulus cells.

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.

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. For his Ph.D., he studied, under the supervision of Menachem (Hemi) Gutman, the respiratory electron transport chain in mitochondria. 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). He did a second postdoctoral fellowship in Madison, Wisconsin, USA where he studied bacterial chemotaxis under the supervision of Julius Adler (1978–1980).

Michael Eisenbach married Lea Eisenbach (née Abarbanel) in 1967, divorced in 1985, and married Michal Schwartz (née Hevrony) in 1991. He has three sons: Shmuel ("Mooli", born 1972), Menachem ("Manny", born 1976), and Tomer (born 1993). He had a sister, Chava Teomi (1940–2012).

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. Michael Eisenbach grew up in Tel Aviv and studied in an evening high school while working during the daytime as a messenger boy (first for the Tel Aviv-Yafo Municipality and then for the Dubek company). He served his compulsory military term in the Israel Defense Forces in 1963–1966.