CORNELIS B. VAN NIEL (1897-1985):

Educator, Pioneer of General Microbiology

King-Thom Chung is a professor of microbiology at the Department of Microbiology and Molecular Cell Sciences, The University of Memphis, Memphis, TN.

In December of 1928, a young Ph.D., Dr. C. B. Van Niel, arrived at the Jacquez Loeb Laboratory of the Hopkins Marine Station belonging to Stanford University and located on the Monterey Peninsula, California. Many of us remembered Dr. Van Niel for his work on photosynthesis. He developed a revolutionary concept of the chemistry of photosynthesis that was to influence research on the topic for many years. He also was the first in the United States to teach "General Microbiology." His teaching resulted in the great blossoming of microbiology in this century. Many distinguished microbiologists including Nobel Laureates, were influenced by him directly or indirectly. Van Niel was the third important figures of the Delft School of microbiology — Martinus W. Beijerinck (1851-1931), Albert J. Kluyver (1888-1956), and Cornelis B. Van Niel (1897-1985). He brought the rich inheritance of the Delft School to this country. To call him a "pioneer of General Microbiology" of this country is very appropriate.

Van Niel was born in Haarlem, The Netherlands, on Nov. 4, 1897. His father, Jan Hendrik Van Niel, died when he was seven years old. He was raised by his mother, Geertien Gesiena Hagen, along with his uncles. They affected his education a great deal. At the age of 15, when his family spent their summer vacation as guests of a friend on a large estate in northern Holland devoted to various agricultural activities, he was impressed by the host who introduced him to methods of agricultural research. He learned that one could raise a question and obtain a more or less definitive answer to it as a result of an experiment. This greatly influenced Van Niel's interest and guided him in the experimental approach of solving scientific problems. In high school, he was greatly influenced by his chemistry teacher Dr. H. Van Erp, and later, he developed a strong interest in chemistry and would set up a small laboratory at home where he analyzed samples of fertilizers in his spare time. Of course, good grades in high school would lead him to enter the Chemistry Division of the Technical University, a prestigious school in the Netherlands, in Delft in 1916. But after only three months, he was inducted into the Dutch Army, in which he stayed until the end of 1918.

In the Army, he was very much disturbed by the rough and impersonal life of the military training. In his memory, he said he was "utterly unaware of the many problems to which man is exposed and with which he must learn to cope." Yet, he was influenced by one of his good friends, Jacques de Kadt, later a famous Dutch sculptor, who introduced Van Niel to a new world of literature, art, and philosophy. Under Jacques’ influence, he read the works of Emil Zola, Anatole France, Henrik Ibsen, August Strindberg, George Bernard Shaw and Friedrich W. Nietzsche . These might have greatly influenced on Van Niel's philosophical thinking during which he called himself "a rebel." But this period might have helped him to become a superlative teacher later on. After quitting the Army, he returned to school and continued his education in chemistry. He took many courses, including G. Van Iterson's course in genetics and plant anatomy and chemistry, and also M. W.Beijerinck's course in general and applied microbiology. Most important of all, he decided to major in Microbiology after hearing the inaugural lecture of A. J. Kluyver, who succeeded Beijerinck in 1921. Here he began his career as a microbiologist.

In 1923, he received Chemistry Engineering degree, and also accepted a position as an assistant to Kluyver. He helped taking care of a large pure culture collections of bacteria, yeasts and fungi, and preparing demonstration in Kluyver's courses. In addition, Van Niel also isolated pure cultures of photosynthetic Chromatium species and Thiosarcina rosea, and demonstrated that oxygen is not produced. (For the purple bacteria, H2S is required for their growth.)

Van Niel expected to continue his study of purple bacteria for his Ph.D. dissertation. In the mean time Van Niel developed an effective method for isolating propionic acid bacteria from Swiss cheese as a side project. But Kluyver suggested that he work on propionic acid bacteria for his Ph.D. dissertation. He agreed. His Ph.D. dissertation was entitled "The Propionic Acid Bacteria" and published in 1928. In this dissertation, he discovered that diacetyl was the compound responsible for the characteristic aroma of high quality butter.

Van Niel came to the U.S.A. in 1928 upon the invitation of L.G.M Baas-Becking (1895-1963), professor of physiology of Stanford University. Van Niel never intended to migrate to the U.S.A. because he did not like the materialism of America Society. However, when Van Niel arrived in Carmel, California, he was immediately impressed by the charm of the town, and the beautiful site the Jacques Loeb Laboratory. He also liked the freedom from outside pressure thatHopkins Marine Station provided. Van Niel loved his job continued his study and never intended to leave even later when he was offered the Chair of the Kluyver professorship of his Alma Mater.

Van Niel continued his study of purple and green bacteria. In his study, he demonstrated that photosynthesis is essentially a light-dependent reaction in which hydrogen from a suitable oxidizable compound reduces carbon dioxide to cellular materials. This can be expressed by:

2 H2A + CO2 --- >2A + CH2O + H2O

According to this formula, H2O is the hydrogen donor in green plant photosynthesis and is oxidized to O2. When H2S or another "oxidizable" sulfur compound is the hydrogen donor for purple and green sulphur bacteria, the "oxidation" product is sulphur or sulphate depending on the organism. In this fashion, the evolution of O2 in the green plant is coming from H2O, not from carbon dioxide. This was later proved by using radioisotopic techniques. This certainly was a "milestone contribution" to the understanding of photosynthesis in general. Van Niel also studied the culture, morphology and physiology of purple and sulphur bacteria, and also the nonsulphur purple and brown bacteria. He classified 150 strains isolated from natural sources into 6 species and two genera, Rhodopseudomonas and Rhodospirillum.

Another great contribution of Van Niel on photosynthesis is how radiant energy participates in photosynthesis. Many investigators considered that radiant energy could be used to activate either carbon dioxide and/or the hydrogen donor. Through extensive study, Van Niel concluded that radiant energy activates the hydrogen donors instead of carbon dioxide. He also concluded that both plant and bacterial photosynthetic reactions have a common reaction; the photolysis of water to a strong reducing agent, and a strong oxidizing agent. He postulated that the reducing agent was used through a series of enzymatic reactions to convert carbon dioxide to cellular constituents; whereas the oxidizing agent was used to generate oxygen in green plant photosynthesis or to oxidize the hydrogen donor in bacterial photosynthesis. This interpretation of the photochemical event laid down the foundation for the current understanding of photosynthesis. The current concept of photosynthesis is that a special type of chlorophyll (rather than water) is considered the source of the light-generated oxidizing and reducing agent Van Niel also made many other contributions to photosynthesis. For example, he did a series of studies of the pigment of the purple and green bacteria, which help us understand the role of pigment in photosynthesis. He also did many cultural works, in physiology, ecology, biochemistry, enzymatic investigation, etc. He often directed, gave encouragement, advice and inspired many of his postdoctoral student, associates or even graduate students to work on different aspects of photosynthesis.

Van Niel's studies of photosynthetic bacteria led him to consider other processes in which carbon dioxide utilization might occur. One of these is methane formation. He postulated that methane formation from organic compounds by anaerobic bacteria was the result of carbon dioxide reduction.

From methanogenesis, Van Niel also discovered that CO2 was utilized by other bacteria, fungi and protozoa. He concluded that carbon dioxide fixation generally occurs bycarboxylation reaction and that carbon dioxide is required to counteract the decarboxylation of oxaloacetate, which "constitutes a leak through which certain essential cell constituents are drained off."

Van Niel also did some work on the chemistry of denitrification. He postulated that nitramide, H2N.NO2 was a possible intermediate of denitrification. He showed that NO3- could serve as an additional electron acceptor in the nitrate adapted Chlorella in photosynthesis.Van Niel's interest in microbial taxonomy started from his Ph.D. dissertation work. He had reviewed the main features of bacterial taxonomy and proposed a possible sequence for the evolution of various morphological types of bacteria. He and A. J. Kluyver formulated a taxonomic system, dividing bacteria into four morphological types defined by cell shape, type of flagella and sporulation. They were subdivided into 63 genera. In 1941, he and R. Y. Stanier (1916-1982) undertook an analysis of the problem of classification of the larger taxonomic units among microorganisms. He considered that morphological characteristics should be given priority over physiological characteristics. In 1961, Van Niel and Stanier defined the procaryotes as cells in which the nuclear material (nucleoplasm) is not surrounded by a nuclear membrane. This definition of procaryotes is still used today.

Perhaps the greatest contribution of Van Niel to microbiology was his teaching. His unusual technique of conveying the scientific message and his extraordinary ability to inspire led the top brains in this country to devote their careers to the development of General Microbiology and Comparative Biochemistry for several decades. His lecture techniques were derived partly from his own teachers, such as Beijerinck and Kluyver, and created from his own talents. His lectures often lasted for several hours and were presented with such clarity and histrionic skill as to capture the complete attention and stimulate the enthusiasm of his students. The lectures sounded as though he delivered universal truth and required the student’s whole attention. No one ever felt tired. Van Niel gave you the impression that you were participating in the most significant part of scientific progress. Every one of his students were so highly inspired and excited that they were willing to devote their whole career to the endeavor of microbiological research. This kind of inspiration and his personal charisma is beyond imagination. For instance, this author listened to his lecture only once, but changed his study concept and decided to choose microbiology as his subject. Some notable scientists would give up their original disciplines and choose to devote themselves to aspects of microbiology for research. Many of his students and postdoctorates became the major pioneers of different fields of microbiology. His influence on the development of microbiology in the United States, particularly on the West Coast, has been tremendous. He is surely the major pioneer in the development of microbiology and comparative biochemistry of our time.

As more microbiological knowledge developed, his lectures expended from three afternoons a week to three days a week, with class hours often extending from eight o’clock in the morning to well into the evening, with time out only for lunch and tea or coffee breaks.

He discussed the metabolism of each group of microorganisms, emphasizing the most recent findings regarding intermediary metabolism, similarities and differences in degradative pathways, and the chemical and enzymatic relationships between degradative metabolism and synthesis of cellular components. He examined the structures of bacterial cells, aspects of bacterial genetics, variation and adaptation, bacterial and yeast taxonomy and also the philosophy of science.

According to Dr. Robert E. Hungate, Van Niel’s first graduate student, Van Neil’s lectures were also accompanied with a series of simple experiments. He was always in the laboratory guiding the work and commenting on each student's observation and results. He would stimulate students to make judgements about the meaning of their observations. Sometimes he intentionally lead them to incorrect conclusions so that in a later experiment, already planned, he would reveal the error. After the experiment, he would make a detailed presentation of its historical background, usually starting with the primitive ideas and progressing to the latest development. He always emphasized possible alternate interpretations of the available information at each phase of scientific investigation. He also lectured on the frequently slow and difficult process of moving from clearly erroneous to more nearly correct, but never immutable conclusion. During the early years, only a few students attended. But as Van Niel’s reputation as a teacher spread, his classes expanded. Initially there were only undergraduate and graduate students from Stanford; later they came from many institutions. There also were auditors of the discussions and lectures, who did not do the experiments, mostly postdoctoral fellows or established scientists who wished to extent their background in general microbiology. The list of students and auditors who attended Van Niel’s lectures between 1938 to 1962 read like a Who’s Who of the biological scientists in the U.S.A. with several other countries. Many of his students became pioneers of some field of microbiology and several were Nobel Prize laureates. Both directly and indirectly through his students, Van Niel exerted a powerful influences on teaching and research on general microbiology for at least a generation.

One of the great merits of Van Niel's teaching is that he was interested in his students. He did not believe in simply directing research. Instead, he encouraged his students or associates to follow their own interests, which were mostly stimulated by him. He would do every thing possible to help the research. The range of research in his laboratory was exceedingly wide, which included the culture and physiology of blue-green algae and diatoms, nutritional and taxonomic studies of plant-pathogenic bacteria, biological methane formation, pteridine and carbohydrate metabolism of protozoa, germination of mold spores, biology of Caulobacteria, cultivation of free-living spirochetes, induction of fruiting bodies in myxobacteria, decomposition of cellulose, the role of microorganisms in the food cycle of aquatic environments, adaptation of bacteria to high salt concentrations, cultivation of spirilla and colorless sulfur bacteria, bacterial fermentations, thermophilic bacteria, denitrification, pyrimidine metabolism and thermodynamic of living systems. To all students Van Niel gave freely of his time, advice and enthusiasm, drawing on his own extraordinary knowledge of the literature. His memory of literature was so powerful that it was like a living dictionary. He often pointed out the most relevant literature of each subject of his interest to the right page number of different journals. But he was seldom willing to become a co-author of the final publication of his students. Therefore many of his scientific contributions are simply embedded in the publications of his students and associates.

Van Niel retired from the Marine Station in 1962, and worked as a visiting profession at the University of California, Santa Cruz from 1964 to 1968. This author was fortunate to meet him at this period and establish a memorable friendship since then. Through his influence, this author became a doctoral student of Dr. Robert E. Hungate (1906-). Most memorable was this author had the honor to be given by Dr. Van Niel in person a copy of his Ph.D. dissertation "The Propionic Acid Bacteria" and also a copy of book by his master A. J. Kluyver entitled "The Chemical Activities of Microorganisms."

In 1972, Van Niel gave up teaching and research entirely and lived quietly with his wife Christina Van Hemert in Carmel, California. Van Niel married his wife on August 17, 1923 in the Netherlands after 8 years of engagement. They raised three children: Ester, Ruth and Jan. They had a wonderful marriage. He died on March 10, 1985, after a life as a great teacher. His success in teaching is a result of his charm of personality, the breadth of his understanding and the comprehensiveness of his memory. Those who knew him, were fully aware that he was a fine man. His warm, kind wisdom and inspiration impressed each mind profoundly and never faded away.