Krebs, Hans Adolf WORLD OF MICROBIOLOGY AND IMMUNOLOGY330•
more than 350 scientific publications. But the story of Krebs’s
life is more than a tally of scientific achievements; his biogra-
phy can be seen as emblematic of biochemistry’s path to
recognition as its own discipline.
In 1900, Alma Davidson Krebs gave birth to her second
child, a boy named Hans Adolf. The Krebs family—Hans, his
parents, sister Elisabeth and brother Wolfgang—lived in
Hildesheim, in Hanover, Germany. There his father Georg
practiced medicine, specializing in surgery and diseases of the
ear, nose, and throat. Hans developed a reputation as a loner at
an early age. He enjoyed swimming, boating, and bicycling,
but never excelled at athletic competitions. He also studied
piano diligently, remaining close to his teacher throughout his
university years. At the age of fifteen, the young Krebs
decided he wanted to follow in his father’s footsteps and
become a physician. World War I had broken out, however,
and before he could begin his medical studies, he was drafted
into the army upon turning eighteen in August of 1918. The
following month he reported for service in a signal corps reg-
iment in Hanover. He expected to serve for at least a year, but
shortly after he started basic training, the war ended. Krebs
received a discharge from the army to commence his studies
as soon as possible.
Krebs chose the University of Göttingen, located near
his parents’ home. There, he enrolled in the basic science cur-
riculum necessary for a student planning a medical career and
studied anatomy, histology, embryology and botanical science.
After a year at Göttingen, Krebs transferred to the University
of Freiburg. At Freiburg, Krebs encountered two faculty mem-
bers who enticed him further into the world of academic
research: Franz Knoop, who lectured on physiological chem-
istry, and Wilhelm von Möllendorff, who worked on histolog-
ical staining. Möllendorff gave Krebs his first research project,
a comparative study of the staining effects of different dyes on
muscle tissues. Impressed with Krebs’s insight that the effi-
cacy of the different dyes stemmed from how dispersed and
dense they were rather than from their chemical properties,
Möllendorff helped Krebs write and publish his first scientific
paper. In 1921, Krebs switched universities again, transferring
to the University of Munich, where he started clinical work
under the tutelage of two renowned surgeons. In 1923, he
completed his medical examinations with an overall mark of
“very good,” the best score possible. Inspired by his university
studies, Krebs decided against joining his father’s practice as
he had once planned; instead, he planned to balance a clinical
career in medicine with experimental work. But before he
could turn his attention to research, he had one more hurdle to
complete, a required clinical year, which he served at the Third
Medical Clinic of the University of Berlin.
Krebs spent his free time at the Third Medical Clinic
engaged in scientific investigations connected to his clinical
duties. At the hospital, Krebs met Annelise Wittgenstein, a
more experienced clinician. The two began investigating
physical and chemical factors that played substantial roles in
the distribution of substances between blood, tissue, and cere-
brospinal fluid, research that they hoped might shed some
light on how pharmaceuticals such as those used in the treat-
ment of syphilispenetrate the nervous system. AlthoughKrebs published three articles on this work, later in life he
belittled these early, independent efforts. His year in Berlin
convinced Krebs that better knowledge of research chemistry
was essential to medical practice.
Accordingly, the twenty-five-year-old Krebs enrolled in
a course offered by Berlin’s Charité Hospital for doctors who
wanted additional training in laboratory chemistry. One year
later, through a mutual acquaintance, he was offered a paid
research assistantship by Otto Warburg, one of the leading bio-
chemists of the time. Although many others who worked with
Warburg called him autocratic, under his tutelage Krebs devel-
oped many habits that would stand him in good stead as his
own research progressed. Six days a week work began at
Warburg’s laboratory at eight in the morning and concluded at
six in the evening, with only a brief break for lunch. Warburg
worked as hard as the students. Describing his mentor in his
autobiography, Hans Krebs: Reminiscences and Reflections,
Krebs noted that Warburg worked in his laboratory until eight
days before he died from a pulmonary embolism. At the end
of his career, Krebs wrote a biography of his teacher, the sub-
title of which described his perception of Warburg: “cell phys-
iologist, biochemist, and eccentric.”
Krebs’s first job in Warburg’s laboratory entailed famil-
iarizing himself with the tissue slice and manometric (pressure
measurement) techniques the older scientist had developed.
Until that time, biochemists had attempted to track chemical
processes in whole organs, invariably experiencing difficulties
controlling experimental conditions. Warburg’s new tech-
nique, affording greater control, employed single layers of tis-
sue suspended in solution and manometers (pressure gauges)
to measure chemical reactions. In Warburg’s lab, the tissue
slice/manometric method was primarily used to measure rates
of respirationand glycolysis, processes by which an organism
delivers oxygen to tissue and converts carbohydrates to
energy. Just as he did with all his assistants, Warburg assigned
Krebs a problem related to his own research—the role of
heavy metals in the oxidation of sugar. Once Krebs completed
that project, he began researching the metabolism of human
cancer tissue, again at Warburg’s suggestion. While Warburg
was jealous of his researchers’ laboratory time, he was not
stingy with bylines; during Krebs’s four years in Warburg’s
lab, he amassed sixteen published papers. Warburg had no
room in his lab for a scientist interested in pursuing his own
research. When Krebs proposed undertaking studies of inter-
mediary metabolism that had little relevance for Warburg’s
work, the supervisor suggested Krebs switch jobs.
Unfortunately for Krebs, the year was 1930. Times were
hard in Germany, and research opportunities were few. He
accepted a mainly clinical position at the Altona Municipal
Hospital, which supported him while he searched for a more
research-oriented post. Within the year, he moved back to
Freiburg, where he worked as an assistant to an expert on
metabolic diseases with both clinical and research duties. In
the well-equipped Freiburg laboratory, Krebs began to test
whether the tissue slice technique and manometry he had mas-
tered in Warburg’s lab could shed light on complex synthetic
metabolic processes. Improving on the master’s methods, he
began using saline solutions in which the concentrations ofwomi_K 5/6/03 3:29 PM Page 330