The use of Beneficial Microorganisms for Corals (BMCs) has been proposed recently as a tool for the improvement of coral health, with knowledge in this research topic advancing rapidly. BMCs are defined as consortia of microorganisms that contribute to coral health through mechanisms that include ( a) promoting coral nutrition and growth, ( b) mitigating stress and impacts of toxic compounds, ( c) deterring pathogens, and ( d) benefiting early life-stage development. Here, we review the current proposed BMC approach and outline the studies that have proven its potential to increase coral resilience to stress. We revisit and expand the list of putative beneficial microorganisms associated with corals and their proposed mechanisms that facilitate improved host performance. Further, we discuss the caveats and bottlenecks affecting the efficacy of BMCs and close by focusing on the next steps to facilitate application at larger scales that can improve outcomes for corals and reefs globally. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Archaeal populations are abundant in cold and temperate environments, but little is known about their potential response to climate change-induced temperature changes. The effects of temperature on archaeal communities in unamended slurries of weakly acidic peat from Spitsbergen were studied using a combination of fluorescent in situ hybridization (FISH), 16S rRNA gene clone libraries and denaturing gradient gel electrophoresis (DGGE). A high relative abundance of active archaeal cells (11-12% of total count) was seen at low temperatures (1 and 5 degrees C), and this community was dominated by Group 1.3b Crenarchaeota and the euryarchaeal clusters rice cluster V (RC-V), and Lake Dagow sediment (LDS). Increasing temperature reduced the diversity and relative abundance of these clusters. The methanogenic community in the slurries was diverse and included representatives of Methanomicrobiales, Methanobacterium, Methanosarcina and Methanosaeta. The overall relative abundance and diversity of the methanogenic archaea increased with increasing temperature, in accordance with a strong stimulation of methane production rates. However, DGGE profiling showed that the structure of this community changed with temperature and time. While the relative abundance of some populations was affected directly by temperature, the relative abundance of other populations was controlled by indirect effects or did not respond to temperature.

Two bacterial strains (DY05(T) and 47666-1) were isolated in Queensland, Australia, from diseased cultured crustaceans Panulirus ornatus and Penaeus monodon, respectively. On the basis of 16S rRNA gene sequence identity, the strains were shown to belong to the Harveyi clade of the genus Vibrio. Multilocus sequence analysis using five housekeeping genes (rpoA, pyrH, topA, ftsZ and mreB) showed that the strains form a monophyletic group with 94.4% concatenated sequence identity to the closest species. DNA-DNA hybridization experiments showed that strains DY05(T) and 47666-1 had 76% DNA similarity to each other, but <70% to their closest neighbours Vibrio harveyi LMG 4044(T) (< or =55%), Vibrio campbellii LMG 11216(T) (< or =52%) and Vibrio rotiferianus LMG 21460(T) (< or =46%). Strains DY05(T) and 47666-1 could be differentiated from their relatives on the basis of several phenotypic characteristics. The major fatty acids were C(15:0) iso 2-OH and/or C(16:1)omega7, C(16:0), C(18:1)omega7 and C(14:0). Based on the polyphasic evidence presented here, it can be concluded that strains DY05(T) and 47666-1 belong to the same novel species of the genus Vibrio, for which the name Vibrio owensii sp. nov. is proposed. The type strain is DY05(T) (=JCM 16517(T)=ACM 5300(T)).