Meet Microbiologist Ruth Ella Moore, the First Black Woman to Earn a PhD in the Natural Sciences

In 1933, Ruth Ella Moore (1903-1994) became the first Black woman to earn a Ph.D. in the natural sciences. The Columbus, Ohio native received her Ph.D. in bacteriology from Ohio State University, where she also finished her B.S. and M.A. Her dissertation was published in two parts: Studies on Dissociation of Mycobacterium Tuberculosis, and A New Method of Concentration of the Tubercle Bacilli as Applied to Sputum and Urine Examination. At the time, tuberculosis was the second largest cause of death and a cure was still more than a decade away.

She later became a professor at Howard University in 1940, and department head in 1952, the first woman to head any department at Howard. One of her first acts as Head was to change the department name from Department of Bacteriology to Department of Microbiology. She retired in 1973.

Here, let’s take a look at some of Moore’s work in microbiology.

Immunology of dental caries

Moore wrote a discussion piece on the immunology of dental caries in 1938, focusing on Bacillus acidophilus (now known as Lactobacillus acidophilus). Prior to the dominance of Streptococcus mutans as the bacterium associated with dental caries, the role L. acidophilus in dental caries was explored as early as 1915. In this article, Moore discusses the contributions of high carbohydrate diets to L. acidophilus growth and the presence of the bacterium in the mouth of caries susceptible patients but not in the mouths of caries-free patients. She also discusses whether there is a substance (ex: antibodies) in the saliva that kills B. acidophilus in caries-free individuals and the possibility of vaccines against L. acidophilus. 

Sensitivity of gut microbes to antibiotics

In 1963, Moore published an article on her studies on microbes isolated from the gut of the death’s head cockroach. She isolated pure cultures from the cockroach gut and cultured them on trypticase soy agar. To determine antimicrobial susceptibility, she placed disks containing antibiotics at various concentrations onto the plates. After incubation, she saw how the antibiotics affected the microbes by looking at the zones of inhibition, areas around the disk where the microbe did not grow. She considered the bacteria sensitive to the antibiotic if there was a zone of inhibition around the disk and resistant if there wasn’t a zone of inhibition around the disk.

But she didn’t stop there. Bacteria can be inhibited by antibiotics because the antibiotic kills the bacteria (bactericidal) or because it inhibits further growth (bacteriostatic). To tease out this difference, Moore removed agar from the zone of inhibition and placed it in nutrient broth. After 24 hours of growth she saw whether the bacteria grew or not. If the broth turned turbid, she considered the effect of the antibiotic bacteriostatic. Once the antibiotic was removed, the bacteria could grow again. If the broth remained clear, the antibiotic was bactericidal. It killed the bacteria on the plate.

More on Moore’s research and teaching

Aside from these research interests, Moore’s research focus included the distribution of blood groups among Black Americans and Enterobacteriaceae. At Howard, she played an active role in the community and was the chair of the scholarship and loans committee and the student guidance committee. She left a lasting impression on Howard University and is honored each year through the university’s Ruth E. Moore and Lloyd H. Newman Service Award.

Moore was a lot of firsts in a time of rampant gender and racial discrimination. In addition to being the first Black woman to earn a Ph.D. in the natural sciences and the first woman to head a department at Howard University, she was also the first Black woman to join the American Society for Microbiology (ASM) in 1936. However, she faced several obstacles. She was not promoted to associate professor for over a decade and there’s no evidence that she became a tenured professor despite her decades of research and teaching.