gene family expansion underpins adaptation to diverse hosts and environments in symbiotic sulfide oxidizers.

Sulfur-oxidizing bacteria (SOB) have developed distinct ecological strategies to obtain reduced sulfur compounds for growth. These range from specialists that can only use a limited range of reduced sulfur compounds to generalists that can use many different forms as electron donors. Forming intimate symbioses with animal hosts is another highly successful ecological strategy for SOB, as animals, through their behavior and physiology, can enable access to sulfur compounds.

Gene loss and symbiont switching during adaptation to the deep sea in a globally distributed symbiosis.

Chemosynthetic symbioses between bacteria and invertebrates occur worldwide from coastal sediments to the deep sea. Most host groups are restricted to either shallow or deep waters. In contrast, Lucinidae, the most species-rich family of chemosymbiotic invertebrates, has both shallow- and deep-sea representatives.

Microbial communities in developmental stages of lucinid bivalves.

Bivalves from the family Lucinidae host sulfur-oxidizing bacterial symbionts, which are housed inside specialized gill epithelial cells and are assumed to be acquired from the environment. However, little is known about the Lucinidae life cycle and symbiont acquisition in the wild. Some lucinid species broadcast their gametes into the surrounding water column, however, a few have been found to externally brood their offspring by the forming gelatinous egg masses.

Natural experiments and long-term monitoring are critical to understand and predict marine host-microbe ecology and evolution.

Marine multicellular organisms host a diverse collection of bacteria, archaea, microbial eukaryotes, and viruses that form their microbiome. Such host-associated microbes can significantly influence the host's physiological capacities; however, the identity and functional role(s) of key members of the microbiome ("core microbiome") in most marine hosts coexisting in natural settings remain obscure. Also unclear is how dynamic interactions between hosts and the immense standing pool of microbial genetic variation will affect marine ecosystems' capacity to adjust to environmental changes.

Global biogeography of chemosynthetic symbionts reveals both localized and globally distributed symbiont groups.

In the ocean, most hosts acquire their symbionts from the environment. Due to the immense spatial scales involved, our understanding of the biogeography of hosts and symbionts in marine systems is patchy, although this knowledge is essential for understanding fundamental aspects of symbiosis such as host-symbiont specificity and evolution. Lucinidae is the most species-rich and widely distributed family of marine bivalves hosting autotrophic bacterial endosymbionts.

The symbiotic 'all-rounders': Partnerships between marine animals and chemosynthetic nitrogen-fixing bacteria.

Nitrogen fixation is a widespread metabolic trait in certain types of microorganisms called diazotrophs. Bioavailable nitrogen is limited in various habitats on land and in the sea, and accordingly, a range of plant, animal, and single-celled eukaryotes have evolved symbioses with diverse diazotrophic bacteria, with enormous economic and ecological benefits. Until recently, all known nitrogen-fixing symbionts were heterotrophs such as nodulating rhizobia, or photoautotrophs such as cyanobacteria.

Organ transcriptomes of the lucinid clam Loripes orbiculatus (Poli, 1791) provide insights into their specialised roles in the biology of a chemosymbiotic bivalve.

Background: The lucinid clam Loripes orbiculatus lives in a nutritional symbiosis with sulphur-oxidizing bacteria housed in its gills. Although our understanding of the lucinid endosymbiont physiology and metabolism has made significant progress, relatively little is known about how the host regulates the symbiosis at the genetic and molecular levels. We generated transcriptomes from four L.

The characterization of sponge NLRs provides insight into the origin and evolution of this innate immune gene family in animals.

The "Nucleotide-binding domain and Leucine-rich Repeat" (NLR) genes are a family of intracellular pattern recognition receptors (PRR) that are a critical component of the metazoan innate immune system, involved in both defense against pathogenic microorganisms and in beneficial interactions with symbionts. To investigate the origin and evolution of the NLR gene family, we characterized the full NACHT domain-containing gene complement in the genome of the sponge, Amphimedon queenslandica. As sister group to all animals, sponges are ideally placed to inform our understanding of the early evolution of this ancient PRR family.

Evolution of the capsular operon of Streptococcus iniae in response to vaccination.

Streptococcus iniae causes severe septicemia and meningitis in farmed fish and is also occasionally zoonotic. Vaccination against S. iniae is problematic, with frequent breakdown of protection in vaccinated fish.