Centre Algatech

The research team of the Laboratory of Anoxygenic Phototrophs at the Institute of Microbiology of the Czech Academy of Sciences (Centre ALGATECH in Třeboň) has received significant international recognition. The bacterium they described, Chloracidobacterium validum, was selected as “Microbe of the Month” by the British Microbiology Society.

The findings led not only to the description of a new species, Chloracidobacterium validum, but also to the establishment of a new genus (Chloracidobacterium), a new family (Chloracidobacteriaceae), and a new order (Chloracidobacteriales). The genus Chloracidobacterium is currently the only known phototrophic representative of the phylum Acidobacteriota. The discovery was published in the journal International Journal of Systematic and Evolutionary Microbiology.

An unusual combination of phototrophic features

Chloracidobacterium validum is a microaerophilic and moderately thermophilic bacterium with an optimal growth temperature of around 45 °C. It belongs to anoxygenic phototrophic organisms – it uses light as an energy source but does not produce oxygen and lacks the ability for autotrophic carbon dioxide fixation, which is typical, for example, of algae and higher plants.

The photosynthetic apparatus of this bacterium includes bacteriochlorophyll c and bacteriochlorophyll a, chlorosomes as light-harvesting structures, the Fenna–Matthews–Olson protein as an energy transfer component, and a homodimeric type-1 reaction center where light energy is converted into chemical energy. This combination of traits is known from green sulfur bacteria, which are strictly anaerobic. In contrast, Chloracidobacterium requires low concentrations of oxygen, and some biosynthetic processes depend on its presence.

This unusual combination of properties makes the genus Chloracidobacterium an important model for studying the evolution of phototrophy.

International collaboration

The new species was isolated during an expedition led by Prof. Michal Koblížek from the Institute of Microbiology of the Czech Academy of Sciences in Třeboň. The bacterium was obtained from a microbial mat in hot springs located in the caldera of the extinct Kozhuh volcano near the town of Rupite in southern Bulgaria.

“The aim of the expedition was to study thermophilic cyanobacteria and their changing species composition depending on the cooling of water in the outflow from the hot vents. Our colleague Dr. Markus Tank from the German Collection of Microorganisms in Braunschweig had experience with thermophilic anoxygenic bacteria from hot springs in the USA, and it was he who succeeded in isolating several interesting bacterial strains. Detailed characterization was subsequently carried out by Dr. Mohit Kumar Saini from the Třeboň laboratory. It was then confirmed that this was not only a new species, but also a representative of a new genus, family, and order,” Prof. Koblížek explained.

In addition to researchers from the Czech Republic and Germany, experts from Japan and the USA also participated in the study.

Cultural and historical context and a Czech footprint

The strain of the new bacterium was designated according to the specific spring BV2. The abbreviation BV refers to the site known as the Baba Vanga sanctuary – a place associated with the famous Bulgarian mystic Baba Vanga, who lived in Rupite. The thermal pools in the area are marked with the abbreviation BV and a number; this microorganism was isolated from pool BV2.

The locality also has another Czech scientific connection – already in the 1980s, the former Czechoslovak Academy of Sciences and the Třeboň branch of the Institute of Microbiology were involved in the construction of a large-scale microalgae cultivation facility there. The current discovery thus symbolically builds on long-standing Czech activities in this region.

Significance beyond the discovery itself

The discovery and description of a new species is not only of taxonomic importance. It provides important insights into the evolution of light-harvesting systems across organisms that utilize solar energy.

Different groups of bacteria have developed distinct strategies for capturing light and converting its energy into a biologically usable form. Comparing chlorosomes, reaction centers, and energy transfer proteins among evolutionarily distant lineages allows a better reconstruction of the development of these mechanisms.

Knowledge gained from basic research may also have broader implications in the future. A detailed understanding of various types of light-harvesting systems may inspire approaches in synthetic biology – for example, in designing modified microorganisms capable of efficiently utilizing light energy. In addition, the complete genome of the bacterium has been described, including genes for the production of lasso peptides, which are being studied in Třeboň as potential next-generation antibiotics.

Research carried out at the Institute of Microbiology of the Czech Academy of Sciences thus contributes not only to our understanding of the evolution of life, but also creates a potential foundation for future biotechnological innovations.