Shielding the Next Generation: Symbiotic Bacteria from a Reproductive Organ Protect Bobtail Squid Eggs from Fungal Fouling

Organisms must have strategies to ensure successful reproduction. Some animals that deposit eggs protect their embryos from fouling/disease with the help of microorganisms. Although beneficial bacteria are hypothesized to contribute to egg defense in some organisms, the mechanisms of this protection remain largely unknown, with the exception of a few recently described systems. Using both experimental and analytical approaches, we demonstrate that symbiotic bacteria associated with a cephalopod reproductive gland and eggs inhibit fungi. Chemical analyses suggest that these bacteria produce antimicrobial compounds that may prevent overgrowth from fungi and other microorganisms. Given the distribution of these symbiotic glands among many cephalopods, similar defensive relationships may be more common in aquatic environments than previously realized. Such defensive symbioses may also be a rich source for the discovery of new antimicrobial compounds.The importance of defensive symbioses, whereby microbes protect hosts through the production of specific compounds, is becoming increasingly evident. Although defining the partners in these associations has become easier, assigning function to these relationships often presents a significant challenge. Here, we describe a functional role for a bacterial consortium in a female reproductive organ in the Hawaiian bobtail squid, Euprymna scolopes. Bacteria from the accessory nidamental gland (ANG) are deposited into the egg jelly coat (JC), where they are hypothesized to play a defensive role during embryogenesis. Eggs treated with an antibiotic cocktail developed a microbial biomass primarily composed of the pathogenic fungus Fusarium keratoplasticum that infiltrated the JC, resulting in severely reduced hatch rates. Experimental manipulation of the eggs demonstrated that the JC was protective against this fungal fouling. A large proportion of the bacterial strains isolated from the ANG or JC inhibited F. keratoplasticum in culture (87.5%), while a similar proportion of extracts from these strains also exhibited antifungal activity against F. keratoplasticum and/or the human-pathogenic yeast Candida albicans (72.7%). Mass spectral network analyses of active extracts from bacterial isolates and egg clutches revealed compounds that may be involved in preventing microbial overgrowth. Several secondary metabolites were identified from ANG/JC bacteria and egg clutches, including the known antimicrobial lincomycin as well as a suite of glycerophosphocholines and mycinamicin-like compounds. These results shed light on a widely distributed but poorly understood symbiosis in cephalopods and offer a new source for exploring bacterial secondary metabolites with antimicrobial activity

Longitudinal distribution of Trichoptera in the Loire River (France) : simple ordination methods and community structure

The longitudinal distribution of Trichoptera at 37 sampling sites along 800 km of the Loire River (France) was analyzed in order to better understand large-scale changes in community structure occurring on a stream continuum. Different simple ordination methods- centered PCA and Correspondence Analysis - were performed to investigate these changes. Both analyses showed that a major change occurs in the community in the upper reaches of the Loire River between the Serre de la Fare and Vorey sampling sites with the appearance of Hydropsyche contubernalis and H.exocellata. Even though other changes in community structure could exist, revealed either by Correspondence Analysis at the first sampling sites (crenal), or by PCA at sampling sites influenced by dams, this Trichoptera community appears to be stable enough in the latter part of the Loire River with the addition of a few species, Hydropsyche bulgaromanorum, Ecnomus tenellus and Ecnomus deceptor, rather than changes in species. The results are discussed in the light of different concepts in stream ecology, and the validity of such data analyses to describe some community patterns. / La distribution longitudinale des trichoptères en 37 points d'échantillonnage le long de 800 kilomètres du fleuve Loire (France) a été analysée afin de mieux comprendre les changements à grande échelle des structures de communauté le long d'un continuum fluvial. Différentes méthodes d'ordination simple - ACP centrée et analyse factorielle des correspondances - ont été réalisées pour examiner ces changements. Les deux types d'analyses ont montré qu'un changement majeur apparaissait dans la communauté dans les stations de l'amont de la Loire entre les sites de Serre de la Fare et Vorey avec l'apparition d'Hydropsyche contubernalis et d'H. exocellata. Même si d'autres changements dans la structure de communauté existent, révélés soit par l'analyse des correspondances factorielles sur les premiers sites de l'amont (crénon), soit par l'ACP sur les sites d'échantillonnages influencés par les barrages, cette communauté de trichopères semble stable surtout dans la partie avale du fleuve Loire avec l'apparition de quelques espèces Hydropsyche bulgaromanorum, Ecnomus tenellus et Ecnomus deceptor, plutôt que des changements spécifiques. Les résultats sont discutés en lumière des différents concepts en écologie des eaux douces, et de la validité de ces types d'analyses pour décrire des modèles de communauté