As the year 2023 comes to an end, it is again time to look at some new bacterial members of our microbial world. As always, the list has been extensive, making it difficult to choose a few interesting bacteria to present. In this #FEMSmicroBlog, Sarah Wettstadt introduces four of the many new bacteria identified in 2023. #FascinatingMicrobes
New brucellosis-causing bacteria from a zoonotic host
Brucellosis is a well-known zoonotic disease. Bacteria from the genus Brucella use various animals as hosts, such as goats, cows, swine, and reindeers. When these bacteria are transmitted to humans, they can cause influenza-like syndromes.
In French Guiana, a new Brucella species was isolated from two independent patients who showed symptoms of fever, lower back pain and fatigue. The isolated strain was named Brucella amazoniensis and is closely related to Brucella suis, which commonly lives in swine, reindeer, dogs and hares. While Brucella suis can cause arthritis and joint pain and even abortion in dogs and swine, in humans it leads to fever and spleen enlargement.
Both infected patients were goldminers, residing in the Amazon rainforest and reporting to have hunted and eaten wild animals. It is suspected that through these they have come into contact with the pathogens. After therapies combining rifampin, doxycycline and gentamycin, both patients were cleared of the pathogens and recovered fully.
New taurine-respiring gut bacterium from mice
As we know, we do not want to get rid of all the bacteria within us. Many bacteria produce beneficial compounds, such as hydrogen sulfide (H2S). At low concentrations, the gas is anti-inflammatory, anti-oxidant and a mitochondrial energy source, and supports the homeostasis of the gut mucosa.
At higher concentrations, however, H2S becomes toxic to organs and tissues. Several gut pathogens, such as Salmonella enterica and Clostridioides difficile, are sulfidogenic and their extensive H2S production can lead to an inflamed mucosa.
For sulfidogenic gut bacteria, taurine is a major substrate and a new study isolated and characterised the sulfidogenic Taurinivorans muris. This bacterium from the genus Desulfovibrionaceae uses taurine as an electron acceptor and lactate, formate, or pyruvate as an electron donor under strict anaerobic conditions.
So far, only the taurine-respiring gut bacterium Bilophila wadsworthia has been known, which uses similar electron donors. Yet, both bacteria have different host preferences: while Bilophila wadsworthia is rather prevalent in human guts, Taurinivorans muris is more abundant in mouse guts.
The study suggests that Taurinivorans muris interacts with both residing gut microbes and pathogens. Taurine, which we mainly obtain from meat, dairy products and fats, reaches the gut linked to bile acids. But as Taurinivorans muris lacks a bile salt hydrolase, it needs other bacteria to liberate taurine before importing and degrading it during anaerobic respiration. The resulting H2S protects from enteric pathogens such as Salmonella enterica and Klebsiella pneumoniae as the molecule directly inhibits enzymes of the aerobic respiration chain.
Bacterial mats from thermal springs as sources for new bacteria
Thermal springs harbour a broad diversity of microbes, some of which are still not cultivated in the lab. A new study sequenced samples from bacterial mats from a sulfide-rich thermal spring in the North Caucasus and used the metagenomic data to assemble the corresponding microbial genomes.
The study identified two potentially new filamentous colourless sulfur-oxidising bacteria from the Thiotrichaceae family as facultative anaerobes and lithoautotrophs. While one strain represents a new species named Thiothrix putei, the second candidate belongs to a new genus and was named Thiocaldithrix dubininis.
Genomic analysis showed that both bacteria encode systems to oxidise thiosulfate to sulfur and sulfate, hydrogen sulfide to elemental sulfur, sulfur to sulfite as well as pathways related to nitrate fixation and reduction and anaerobic respiration. Yet, these metabolic pathways still require experimental validation.
Similar to other members of the Thiotrichaceae family, both bacteria encode two types of energy converters: one using pyrophosphate and one using ATP. Additionally, these systems seem to be Na-dependent instead of H-dependent. The researchers suggest this may save energy, since at higher temperatures, fluid membranes leak more H+ than Na+.
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If you’ve read this far it seems you have an interest in bacteria! Make sure to check out the latest research in FEMS Microbiology Letters to learn even more.
Dr Sarah Wettstadt is a microbiologist-turned science writer and communicator publishing for professional associations and life science organisations. She runs the blogs BacterialWorld, to share the diverse and colourful activities of microbes and bacteria, and Sunny Scientist, to support researchers in their busy scientific days. As science communication manager for the Scientific Panel on Responsible Plant Nutrition and blog post commissioner for the FEMSmicroBlog, Sarah writes about microbiology and plant nutrition research for expert and non-expert audiences. To coach and mentor scientists in science communication, she co-founded the Partnership Business SciComm Society. Previous to her science communication career, Sarah did a PhD at Imperial College London, UK, and a postdoc at the CSIC in Granada, Spain. In her non-scicomm time, she travels the world or enjoys the sunny beaches in Spain playing beach volleyball.
About this blog section
The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.
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