Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Buffer

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The most effective way to prevent bubonic plague is the

maintenance of adequate sanitary conditions. This acts to con-

trol the rodent population, especially in urban centers.

See alsoBacteria and bacterial infection; Epidemics and pan-

demics; Zoonoses

BBuchanan, Robert EarleUCHANAN, ROBERTEARLE(1883-1972)

American microbial taxonomist

Robert Earle Buchanan’s contributions to the wider world of

microbiology involve the classification of microorganisms

and his activity in the expansion of the Society of American

Bacteriologists. This expansion was one of the important

events that led the Society to become the American Society

for Microbiology, the paramount microbiology society in the

world.

Buchanan was educated at Iowa State University and

subsequently became a faculty member there. He received a

B.S. degree in 1904, and a M.S. degree in 1906. After joining

the faculty, he became the first head of the Bacteriology

Department in 1910. He remained head until his retirement in

1948. He was also the first dean of Industrial Science, first
      dean of the Graduate College (1919–1948), and was Director
      of the Agriculture Experiment Station from 1933 until 1948.
      In his research life, Buchanan was a microbial taxono-
      mist, concerned with the classification of microorganisms.
      This interest led him to serve on the Board of Trustees of the
      Bergey’s Manual of Determinative Bacteriology, and to
      assume the responsibilities of co-editor of the eighth edition of
      the manual in 1974. The Manual is the definitive reference
      volume on bacterial classification. Buchanan was also one of
      the founders of the International Bulletin of Bacterial
      Nomenclature and Taxonomyin 1951. He served on the first
      editorial board of the journal. The journal is still published,
      now as the International Journal of Systematic and
      Evolutionary Bacteriology.
      In 1934, the Society of American Bacteriologists began
      the process of expansion by adding a branch that represented
      bacteriologists in Iowa, Minnesota, North Dakota, South
      Dakota, and Wisconsin. Buchanan became the first President
      of the Northwest Branch of the Society in 1935.
      Buchanan also founded the Iowa State Journal of
      Sciencein 1926. The journal was intended as a forum for the
      rapid publication of research papers that were too lengthy for
      publication in other scientific journals. The journal published
      works from the biological and agricultural sciences and, in
      1972, research from the humanities. The journal ceased publi-
      cation in 1988.
      Another landmark publication of Buchanan was in


1949. Then, he published an essay listing the correct Latin
      forms of chemical elements and compounds that are used in
      the naming of bacteria, yeasts, many filamentous fungiand
      some protozoa. This article has proven vital to several gener-
      ations of bacterial taxonomists.
      Buchanan was also active in other international agen-
      cies, including the National Research Council, Inter-American

Institute of Agricultural Sciences, the President’s Committee

on Foreign Aid. His service on missions to Greece, the Middle

East, and India spread agricultural technology and knowledge

of microbiological diseases of agricultural crops around the

developing world.

BUDDING •seeYEAST

BBufferUFFER

A buffer is a solution that resists changes in pHupon the addi-

tion of acid or base. Buffers typically contain several species

that react with added acid and base.

Buffers are important in maintaining the proper envi-

ronment within microorganisms and within other cells,

including those in man. In the microbiology laboratory, many

solutions and growth media are buffered to prevent sudden

and adverse changes in the acidity or alkalinity of the envi-

ronment surrounding the microorganisms.

Blood is an example of a natural buffer. In water, small

volumes of an acid or base solution can greatly change the pH

(measure of the hydrogen ion concentration). If the same

amount of the acid or base solution is added to blood, the nor-

mal pH of the blood (7.4) changes only marginally. Blood and

many other bodily fluids are naturally buffered to resist

changes in pH.

In order to explain the properties of a buffer, it is useful

to consider a specific example, the acetic acid/acetate buffer

system. When acid (e.g., HCl, hydrochloric acid) is added to

this buffer, the added hydronium ion (H+) reacts with the

strongest base in the medium, namely the acetate ion, to form

more acetic acid. This reaction uses up the added hydronium

ion, preventing the pH from rising drastically, and is responsi-

ble for the buffering effect. As a result of adding acid to the

buffer, the concentration of acetate decreases and the concen-

tration of acetic acid increases. The solution acts as a buffer

because nearly all of the added hydronium ion is consumed by

reaction with acetate. As the hydrogen ion concentration

increases, the acetate concentration and acetic acid concentra-

tion must adjust. The pH changes slightly to reflect the shift in

the concentrations, but the change is much smaller than in the

absence of the buffer because most of the added acid is con-

sumed by its reaction with the acetate ion. This example of an

acetic acid/acetate ion buffer is typical of other buffer systems.

Buffers are vitally important in living prokaryotic and

eukaryotic systems. The rates of various biochemical reactions

are very sensitive to the availability of hydronium ions. Many

biochemical reactions (e.g., metabolism, respiration, the trans-

mission of nerve impulses, and muscle contraction and relax-

ation) take place only within a narrow range of pH.

An important buffer in the blood is the bicarbonate ion

and dissolved carbon dioxide in the form of carbonic acid. The

acidity or alkalinity of the blood can be altered by the inges-

tion of acidic or basic substances. The carbonate/bicarbonate

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