In brackish or salt water, vibrio bacteria can be found swimming freely or coexisting with fish, crustaceans, mollusks, and corals as pathogens or symbionts. With global warming, outbreaks in marine animals are expected to increase in frequency due to the relatively high temperatures at which these bacteria grow.
According to a recent study that was published in Frontiers in Microbiology, Vibrio bacteria are responsible for mortality outbreaks in dark-stinging sponges.
Along the Turkish Aegean coast, 117 dark stinging sponges were examined by researchers. Every sponge was measured, captured on camera, and subjected to DNA analysis. Sixty-four percent of the sponges seemed healthy, whereas 27 percent had obvious signs of partial necrosis and nine percent looked dead or dying.
Three different Vibrio species—V. fortis, V. owensii, and V. gigantis—were discovered by scientists through the identification of ribosomal RNAs that are only detected in sick, dying, and dead sponges. Since none of these species were present in all of the diseased sponges under investigation, it is possible that vibrosis is a secondary infection that exacerbates the disease’s progression.
The researchers concluded that the heat-loving Vibrio bacteria functioned as a primary or secondary agent as they were unable to detect the sickness after October.
According to first author Egzi Dinçtürk of Izmir Katip Celebi University, “marine ecosystems, including water temperature, are currently affected due to climate change.” The dynamics of disease in sponges and their pathogens seem to be impacted by these modifications.
In the future, the team hopes to find out if other marine mass mortality occurrences are caused by the same infections. Marine ecosystem protection depends on the early detection and containment of disease outbreaks such as those observed in black stinging sponges.
Named for the vibrating motion they make when swimming, vibrio bacteria comprise over 150 species. In brackish or salt water, the majority of Vibrio can be found swimming freely or as pathogens or symbionts in fish, crustaceans, mollusks, and corals. Because Vibrio prefers rather high temperatures, it is anticipated that as the world warms, outbreaks in marine creatures may occur more frequently. In recent times, Vibrio has been associated with the global ‘bleaching’ of tropical and subtropical corals.
Researchers from Spain and Turkey have now demonstrated that Vibrio bacteria are also involved in mortality epidemics of the dark stinging sponge (Sarcotragus foetidus), a sessile marine creature that is unrelated to humans. Published in Frontiers in Microbiology are the findings.
“This study demonstrates the prevalence of pathogenic Vibrio bacteria in sick individuals of the dark stinging sponge, amid a fatal outbreak initially detected in the Aegean Sea in late 2021,” stated Dr. Manuel Maldonado, a co-author of the research and a senior scientist at the Spanish National Research Council (CEAB-CSIC).
First mentioned in Aristotle’s writings, the black stinging sponge is found throughout the North Atlantic and Mediterranean, usually at shallow depths. Co-author Dr. Fikret Öndes, an associate professor at Izmir Katip Celebi University, first became aware of the mystery sickness affecting the local black stinging sponges in the summer of 2021.
“When I dived and observed the study area and its surroundings, I encountered not only visibly unhealthy sponges but also dead ones,” stated Öndes. He notified his colleagues right away, and together they set out to investigate this new illness.
Subsequent dives off the Turkish Aegean coast of Seferihisar, between August and December, allowed the researchers to examine 117 dark stinging sponges. Every person was measured, captured on camera, and had tissue samples collected for DNA testing. Sixty-four percent of the sponges were healthy, while twenty-seven percent had obvious partial necrosis, and nine percent looked dead. Three Vibrio species—V. fortis, V. owensii, and V. gigantis—were identified by scientists using ribosomal RNAs that are only found in sick, dead, and dying sponges. It was previously recognized that these species may be found in the tissues of diseased crustaceans, prawns, and corals, respectively.
“In all of the sick sponges examined, none of the three harmful Vibrio species were found. This could imply that vibriosis is not the main etiological agent, but rather a secondary infection that exacerbates the disease’s progression. To address this, more study based on the metagenomics of sick people, sampled at many illness stages, is needed, according to Maldonado.