An interview with Professor Aharon Oren

October 2019

Professor Aharon Oren is a List Editor and former Editor-in-Chief for the International Journal of Systematic and Evolutionary Microbiology at the Society. He is heavily involved in matters regarding prokaryote nomenclature and is passionate to continue his work in the field and educate other scientists about the importance of taxonomy. Here, he talks about his career and involvement with the Microbiology Society.

Tell us a little about your area of research and your current role.

Nowadays I am very busy as Editor and reviewer for a large number of journals and other scientific publications. In addition, issues connected with nomenclature of micro-organisms demand more and more of my time. I was recently appointed Editor-in-Chief of the International Code of Nomenclature of Prokaryotes, and this new task will keep me busy for some years. Still, I consider myself a microbial ecologist (and not a taxonomist, as many people may think) who loves exploring the diversity, way of life, and mutual interactions of micro-organisms in natural ecosystems, especially hypersaline ones. ‘Salt’ is the keyword in most of my research since the early 1980s. In addition, being a university professor at the Hebrew University of Jerusalem, I teach courses in general microbiology, environmental microbiology and marine microbiology - the latter at our field station in Eilat at the shore of the Red Sea.

What encouraged you to pursue a career in the field of microbiology?

During my last years of high school, it was very clear to me that I do not want to become a businessman like my father. Fortunately, my parents left me the freedom to choose my own career. At the time, I was very much interested in the plant world, and knew most of the Latin names of the wild plants I found in the Netherlands where I was born. Therefore, I started my biology studies at the University of Groningen in 1969 with the intention to pursue a career in plant science. During the first-year microbiology course taught by Hans Veldkamp I realized that the bacterial world is much more exciting than the world of plants and animals. Plants do little except fixing carbon dioxide while splitting water with the formation of oxygen, powered by sunlight. The animal world does little else besides burning sugars, amino acids and a few other simple carbon compounds, using oxygen as the electron acceptor. The microbes, and especially the prokaryotes, have endless ways of making a living. Micro-organisms can exploit nearly any reaction that is thermodynamically feasible to obtain energy, and they can use about any carbon source available in nature. Sergei Winogradsky and Martinus Beijerinck soon became my role models, and I have enjoyed exploring microbial diversity ever since.

Can you tell us about your biggest professional achievement(s)?

As a M.Sc. student (in Groningen) and as a Ph.D. student (in Jerusalem), I worked on sulfur metabolism of photosynthetic purple bacteria and cyanobacteria, respectively. Soon after having finished my Ph.D. I got the opportunity to study the microbiology of the Dead Sea. In that period there were plans to construct a water carrier between the Mediterranean Sea and the Dead Sea to gain hydroelectric energy. The feasibility of a similar project to connect the Dead Sea with the Red Sea is still being evaluated today. Thus, studies of the Dead Sea became important, and I joined to explore the microbiological aspects of the lake. When I started this work in 1980, little was known about the organisms inhabiting the lake and their dynamics. For several decades I studied the Dead Sea and obtained an insight how this ecosystem functions and what biological changes can be expected to occur if indeed large amounts of seawater will enter the hypersaline Dead Sea.

My interest in hypersaline life in the Dead Sea soon expanded to more general studies of hypersaline ecosystems and the organisms inhabiting them. These studies led to a general theory based on bioenergetic constraints, explaining why some types of microbial metabolism can function up to the highest salinities, while other microbial processes cease to function already at relatively low salt concentrations.

I am greatly pleased that my work on different aspects of microbiology found recognition by a number of institutions abroad. I was granted honorary doctorates of four universities: Osnabrück – Germany, Charles University Prague – Czech Republic, Ljubljana – Slovenia, and (soon) Babeş-Bolyai University, Cluj-Napoca, Romania. In addition, I was elected as an honorary member of the Academia Românǎ in Bucharest.

One of your research areas has a focus on halobacteria, why are they of such interest to your studies?

I have noticed that microbiologists often develop a special affection for the organisms they study. I first got acquainted with the class Halobacteria, often referred to as Haloarchaea, when I started studying the microbiology of the Dead Sea in the early 1980s. It is not difficult to fall in love with this group of organisms. First, they are colourful. The red blooms I witnessed in the Dead Sea in 1980 and in 1992 were due to haloarchaea, and they are mainly responsible for the pink-red colour of saltern crystallizer brines and of the north arm of Great Salt Lake, Utah. The colour is due to special carotenoids that protect the cells against damage by high light intensities, but bacteriorhodopsin and other retinal proteins can also contribute. These retinal proteins enable the cells to use sunlight as a source of energy, even if they cannot lead an autotrophic life style. Second, they have interesting ways of adaptation to life at high salt concentrations. In contrast to most halophilic and halotolerant representatives of the Bacteria, the haloarchaea use potassium chloride to balance the cells’ interior with the high salinity of the brines in which they live. Accordingly, their entire intracellular machinery must be able to function in molar concentrations of KCl. The price they pay for being adapted to life at high salt is their inability to function in low-salt environments. Third, of all groups of Archaea the members of the class Halobacteria are the easiest to grow and to handle, and genetic manipulation systems have been developed for some species, so that they are the ideal model organisms for studying the biology of the archaeal domain.

You are a nomenclature reviewer for the International Journal of Systematic and Evolutionary Microbiology. Why is nomenclature so important?

“Microbiologists who have occasion to use the scientific names of the micro-organisms with which they deal generally prefer to use correct names and use them correctly.” This opens the foreword to the first edition (1958) of the International Code of Nomenclature of Bacteria and Viruses, the precursor of today’s International Code of Nomenclature of Prokaryotes, the document that contains the internationally accepted rules that regulate the naming of prokaryotic taxa. Most microbiologists care little, if at all, about names of micro-organisms. On several occasions I asked senior scientists who study Pseudomonas aeruginosa about the meaning of its specific epithet; nobody gave me the correct answer (aeruginosa = copper rust-coloured). There is a meaning and a story behind the scientific name of every micro-organism.

My interest in scientific names started during my high school period, when I was fascinated by the plant world. The fact that Latin and Greek were both part of my high school curriculum was very useful here. During my early years as a scientist and university teacher I thought little about names of prokaryotes, except when I and my co-workers wanted to describe new species of halophilic micro-organisms, we had isolated and we needed to propose suitable names for them.

About twenty years ago I developed a renewed interest in nomenclature when I joined the Editorial Board of the International Journal of Systematic and Evolutionary Microbiology (IJSEM). In 2002 I also accepted the position of chairman of the International Committee on Systematics of Prokaryotes (ICSP), the committee responsible for the code of nomenclature. At that time all nomenclature quality control was done by two eminent microbiologists who at the same time were great classics scholars: Jean-Paul Euzéby (Toulouse) and Hans-Georg Trüper (Bonn). I learned a lot from my interactions with the late Prof. Trüper, who became my role model in those years.

With the description of more than a thousand new species of prokaryotes annually in recent years, knowledge of the rules of the code of nomenclature is essential to prevent chaos in the literature. Unfortunately, the number of experts who understand microbiology and also have an interest for the classical languages, have studied the rules of the code of nomenclature, and (most important!) have plenty of time to devote to correcting malformed names or giving counsel to confused colleagues, is very small. The workload is getting ever larger: new taxa are described at an ever-increasing rate, and most such descriptions come from China, South Korea, and other Asian countries, where Latin and Greek were never taught in schools.

Names of micro-organisms became to some extent an obsession to me. I enjoy checking proposed names of new taxa for the IJSEM and for a number of other journals and proposing suitable names for micro-organisms to prospective authors who consult me. I also have held one- or two-day workshops about nomenclature in China, India, and South Korea. Teaching nomenclature-Latin and nomenclature-Greek to a group of nearly two hundred young Chinese scientists and students is an interesting challenge!

Why is being involved with the Society journals important to you?

The IJSEM is a unique journal: as the official journal of the International Committee on Systematics of Prokaryotes it provides the only framework where names of new taxa of prokaryotes can be validly published. Many other journals publish descriptions of new species, genera, and higher taxa of Bacteria and Archaea, but to obtain standing in the nomenclature, the names must afterward be validated by publication in the IJSEM. I have always considered it a special honour having been invited to join its Editorial Board. Also, after my five-year term as Editor-in-Chief ended in 2017, I remained involved in the journal as one of its List Editors and as a nomenclature reviewer. Jointly with my colleague George Garrity of Michigan State University I annually produce twenty lists for the journal: the monthly Notification Lists that provide a record of all new names of prokaryotic taxa published in an earlier issue of the IJSEM, the bimonthly Validation Lists that include names of prokaryotic taxa earlier published in other journals so that the names will become validly published and obtain standing in the nomenclature, and two Lists of Changes in Taxonomic Opinion previously published outside the IJSEM. The nomenclature reviewers check the proposed names of all new taxa of micro-organisms in papers submitted to the IJSEM. Thus, more than a thousand papers pass our desks every year. It is a lot of work, but since I am fascinated by the scientific names of microbes, I hope to continue this activity for many more years.

Why did you join the Microbiology Society?

Because of my work as Editor for the IJSEM. The IJSEM differs from the other journals published by the Microbiology Society, as the Society does not actually own the journal. The Society publishes the journal for the Bacteriology and Applied Microbiology Division of the International Union of Microbiological Societies in conjunction with the ICSP. Until the end of 1997 the journal (then still named the International Journal of Systematic Bacteriology) was published by the American Society for Microbiology (ASM). When the ASM was no longer interested in publishing the journal, the Society for General Microbiology, now the Microbiology Society, agreed to continue its publication. Eighteen years ago, when I was elected a member of the Editorial Board, I became impressed by the high professional level of the staff of the Society that produced the journal and by their commitment to improve its standards. I considered it as my moral duty to support the Society that does such a great job for the IJSEM, and therefore I registered as a member.

Have you taken part in any activities as a member of the Society?

Since I was appointed as an Editor of the IJSEM in 2001 and served a term as its Editor-in-Chief from 2012 until 2017, I attended the annual meetings of the Editorial Board. In recent years these meetings were held at the headquarters of the Society at Charles Darwin House in London, but before the Society’s offices moved from Reading to London, our Editorial Board meetings used to be held during the annual conferences organised by the Society or at other international scientific meetings. I thus had the pleasure of attending a few of the Society’s Annual Conferences, and I was impressed by the excellent science and the high level of involvement of the Society’s members in these events. During my tenure as Editor-in-Chief of the journal, I also served as an ex officio member of the Society’s Publishing Committee, and I regularly attended the meetings of that committee.