Credit: (OSU College of Science)
CORVALLIS, Ore. – Corals that appear healthy are more prone to getting sick when they’re home to too many parasitic bacteria, new research at Oregon State University shows.
Supported by the National Science Foundation, the study, published in Environmental Microbiology, adds fresh insight to the fight to save the Earth’s embattled coral reefs, particularly those in the Caribbean.
“The clear relationship we’ve discovered between this kind of bacteria and disease resistance in Caribbean staghorn coral is a crucial piece of the puzzle for coral restoration efforts in that region,” said study co-author Becca Maher, a Ph.D. candidate at Oregon State.
Found in less than 1% of the ocean but home to nearly one-quarter of all known marine species, coral reefs help regulate the sea’s carbon dioxide levels and are a crucial hunting ground that scientists use in the search for new medicines.
Between 2014 and 2017, more than 75% of the world’s reefs experienced bleaching-level heat stress, and 30% suffered mortality-level stress. Bleaching refers to the breakdown of the symbiotic relationship between corals and the algae they rely on for energy.
A complex composition of dinoflagellates, viruses, fungi, bacteria and archaea make up the coral microbiome, and shifts in microbiome composition are connected to changes in coral health.
In 2019, scientists in the lab of OSU microbiologist Rebecca Vega Thurber identified a new genus of parasitic bacteria that flourishes when reefs become polluted with nutrients, siphoning energy from the corals and making them more susceptible to disease.
The bacteria are in the order Rickettsiales, and the new genus is associated primarily with aquatic organisms. Scientists named the genus Candidatus Aquarickettsia and the coral-associated species in the 2019 study, Candidatus A. rohweri, was the first in the new genus to have its genome completely sequenced.
Since their first appearance 425 million years ago, corals have branched into more than 1,500 species, including the one at the center of this research: the critically endangered Acropora cervicornis, commonly known as the Caribbean staghorn coral.
“The bacterial genus we’ve identified is found around the world and in multiple types of corals, but is most notably found in high abundance in the microbiomes of Caribbean staghorn coral,” said study co-author Grace Klinges, also a Ph.D. candidate in the Vega Thurber lab. “Now we’ve uncovered significant evidence that a high abundance of Ca. Aquarickettsia is a marker of disease susceptibility in corals that otherwise seem healthy.”
Disease-resistant corals were found to host a much more even mix of many types of bacteria, she said. Additionally, as corals experienced heat stress from a warming ocean, the microbiome dominance of Ca. Aquarickettsia eroded.
“That’s apparently because the bacteria rely on host nutritional resources that become scarce during periods of stress,” Vega Thurber said. “And then the sudden loss of a dominant community member frees up niche space and creates openings for opportunistic pathogens to proliferate and sicken the coral.”
Erinn Muller of the Mote Marine Laboratory in Sarasota, Florida, led the study.
Rebecca Vega Thurber
Related Journal Article
"Korali zinazoonekana kuwa na afya nzuri huwa na uwezekano mkubwa wa kuugua zinapokuwa na bakteria nyingi za vimelea, ""utafiti mpya katika Chuo Kikuu cha Jimbo la Oregon unaonyesha." Utafiti huo, uliofanywa na Shirika la Sayansi la Marekani, unaongeza ufahamu mpya katika mapambano ya kuokoa matumbawe ya dunia, hasa yale ya Karibea. "Uhusiano ulio wazi ambao tumegundua kati ya aina hii ya bakteria na upinzani wa magonjwa katika matumbawe ya Caribbean staghorn ni kipande muhimu cha fumbo kwa juhudi za kurudisha matumbawe katika mkoa huo, "alisema mwandishi mwenza wa utafiti Becca Maher, mgombea wa PhD katika Jimbo la Oregon." Zipo katika sehemu ndogo ya bahari lakini ni makao ya karibu robo ya spishi zote za baharini zinazojulikana, matumbawe husaidia kudhibiti viwango vya kaboni dioksidi baharini na ni uwanja muhimu wa kuwinda ambao wanasayansi hutumia kutafuta dawa mpya. Kati ya mwaka 2014 na 2017, zaidi ya asilimia 75 ya matumbawe ya dunia yalikabiliwa na shinikizo la joto la kiwango cha kupunguzwa, na asilimia 30 walipata shinikizo la kiwango cha vifo. Kupungua kwa rangi ya matumbawe ni kuharibika kwa uhusiano kati ya matumbawe na mwani ambao hutumiwa kama nishati. Dinoflagellates, virusi, fungi, bakteria na archaea hufanyiza microbiome ya matumbawe, na mabadiliko katika muundo wa microbiome yanahusiana na mabadiliko katika afya ya matumbawe. Katika mwaka wa 2019, wanasayansi katika maabara ya OCS microbiologist Rebecca Vega-Thurber walitambua jamii mpya ya bakteria ya vimelea ambayo hufanikiwa wakati miamba inapochafuliwa na virutubisho, ikichukua nishati kutoka kwa matumbawe na kuwafanya wawe rahisi zaidi kuambukizwa. Bakteria hizo ni za jamii ya Rickettsiales, na jamii hiyo mpya inahusianishwa hasa na viumbe wa majini. Candidatus aquarictus, ambayo ni aina ya korali ya aina ya A. roheri, ni aina ya korali ya asili ya Afrika Kusini ambayo imepatikana katika mimea ya bahari. Tangu kuonekana kwa mara ya kwanza miaka milioni 425 iliyopita, matumbawe yameenea katika spishi zaidi ya 1,500, ikiwa ni pamoja na moja katika kituo cha utafiti huu: Acropora cervicornis, inayoathiriwa sana, inayojulikana kama Caribbean staghorn. "Jini ya bakteria ambayo tumegundua hupatikana ulimwenguni kote na katika aina nyingi za matumbawe, lakini hasa hupatikana kwa wingi katika microbiomes ya matumbawe ya Caribbean staghorn, "alisema mwandishi mwenza wa utafiti Grace Klinges, pia mgombea wa PhD katika maabara ya Vega Thurber. " <unk>Sasa tumegundua ushahidi muhimu kwamba wingi wa Ca. "Akariketsia ni alama ya kuathiriwa na magonjwa katika matumbawe ambayo kwa vyovyote vile yanaonekana kuwa na afya, ""aliongeza, ""matumbawe yanayopinga magonjwa yaligunduliwa kuwa na mchanganyiko sawa zaidi wa aina nyingi za bakteria.""" Kwa kuongezea, kama matumbawe uzoefu joto mkazo kutoka bahari joto, microbiome utawala wa Ca. Aquarickettsia iliharibiwa. "Hiyo ni kwa sababu bakteria hutegemea rasilimali za lishe za mwenyeji ambazo huwa chache wakati wa vipindi vya mkazo", Vega Thurber alisema. "Kisha, kupoteza kwa ghafla kwa mshiriki wa jamii ya kipekee hufungua nafasi ya niche na kuunda nafasi kwa vimelea vya ugonjwa wa fursa kuenea na kuambukiza matumbawe. "" - Erin Muller wa Maabara ya Bahari ya Mote huko Sarasota, Florida, aliongoza utafiti huo." Rebecca Thurber Makala ya Jarida inayohusiana