Microbiota Composition and Evenness Predict Survival Rate of Oysters Confronted to Pacific Oyster Mortality Syndrome

Abstract

Pacific Oyster Mortality Syndrome (POMS) affects Crassostrea gigas oysters worldwide and causes important economic losses. Disease dynamic was recently deciphered and revealed a multiple and progressive infection caused by the Ostreid herpesvirus OsHV-1 µVar, triggering an immunosuppression followed by microbiota destabilization and bacteraemia by opportunistic bacterial pathogens. However, it remains unknown if microbiota might participate to protect oysters against POMS, and if microbiota characteristics might be predictive of oyster mortalities. To tackle this issue, we transferred full-sib progenies of resistant and susceptible oyster families from hatchery to the field during a period in favor of POMS. After 5 days of transplantation, oysters from each family were either sampled for individual microbiota analyses using 16S rRNA gene-metabarcoding or transferred into facilities to record their survival using controlled condition. As expected, all oysters from susceptible families died, and all oysters from the resistant family survived. Quantification of OsHV-1 and bacteria showed that 5 days of transplantation were long enough to contaminate oysters by POMS, but not for entering the pathogenesis process. Thus, it was possible to compare microbiota characteristics between resistant and susceptible oysters families at the early steps of infection. Strikingly, we found that microbiota evenness and abundances of Cyanobacteria (Subsection III, family I), Mycoplasmataceae, Rhodobacteraceae, and Rhodospirillaceae were significantly different between resistant and susceptible oyster families. We concluded that these microbiota characteristics might predict oyster mortalities.

Plant Microbiomes: Do Different Preservation Approaches and Primer Sets Alter Our Capacity to Assess Microbial Diversity and Community Composition?

“…Primer selection is one of the key factors in microbiome analyses. Primer pairs 341F/805R and 515F/806R are widely accepted for bacterial community analysis from human, insects, soil, plant and marine species ( Caporaso et al., 2011 ; Caporaso et al., 2012 ; Jakobsson et al., 2014 ; Delgado-Baquerizo et al., 2016 ; Walters et al., 2016 ; Gomez-Polo et al., 2017 ; Hamonts et al., 2018 ; Clerissi et al., 2020 ), while primer pair 799F/1193R has a two-base pair mismatch for chloroplast ( Chelius and Triplett, 2001 ), which is more suitable for plant microbiome analysis.…”

“…Primer selection is one of the key factors in microbiome analyses. Primer pairs 341F/805R and 515F/806R are widely accepted for bacterial community analysis from human, insects, soil, plant and marine species (Caporaso et al, 2011;Caporaso et al, 2012;Jakobsson et al, 2014;Delgado-Baquerizo et al, 2016;Walters et al, 2016;Gomez-Polo et al, 2017;Hamonts et al, 2018;Clerissi et al, 2020), while primer pair 799F/1193R has a two-base pair mismatch for chloroplast (Chelius and Triplett, 2001), which is more suitable for plant microbiome analysis. However, plant microbiome studies usually require both soil and plant microbiome profiles to connect underground and aboveground microbial communities (Liu et al, 2017;Hamonts et al, 2018), which essentially need consistency with primer selections.…”

The Pacific Oyster Mortality Syndrome, a Polymicrobial and Multifactorial Disease: State of Knowledge and Future Directions

“…In another study, the Mycoplasmataceae, Rhodospirillaceae, and Vibrionaceae bacterial families, as well as the Photobacterium genus, were associated with susceptible oyster families ( 96 ). The proportion of specific taxa, including Cyanobacteriaceae, Colwelliaceae, and Rhodobacteraceae, was significantly higher in resistant oyster families that survived POMS after transplant into the field during an infectious period.…”

“…The proportion of specific taxa, including Cyanobacteriaceae, Colwelliaceae, and Rhodobacteraceae, was significantly higher in resistant oyster families that survived POMS after transplant into the field during an infectious period. Resistant oysters also displayed a higher evenness of the bacterial colonizers, suggesting that a decrease in microbial diversity may be associated with a loss of microbiota function, which could allow colonization by opportunistic pathogens ( 96 ).…”

Host Defense Effectors Expressed by Hemocytes Shape the Bacterial Microbiota From the Scallop Hemolymph

“…If this balance is disrupted, pathogenic microorganisms can proliferate causing damage and host mortality ( 22 , 31 ). In the oyster Crassostrea gigas , microbiota destabilization caused by viral infection and subsequently host immunosuppression ended in bacteremia and host death ( 32 ). In addition, differential basal expression of immune genes has been related with oyster resistance to this polymicrobial disease ( 33 ).…”