Cold-Active Shewanella glacialimarina TZS-4T nov. Features a Temperature-Dependent Fatty Acid Profile and Putative Sialic Acid Metabolism

Species of genus Shewanella are among the most frequently identified psychrotrophic bacteria. Here, we have studied the cellular properties, growth dynamics, and stress conditions of cold-active Shewanella strain #4, which was previously isolated from Baltic Sea ice. The cells are rod-shaped of ~2μm in length and 0.5μm in diameter, and they grow between 0 and 25°C, with an optimum at 15°C. The bacterium grows at a wide range of conditions, including 0.5–5.5% w/v NaCl (optimum 0.5–2% w/v NaCl), pH 5.5–10 (optimum pH 7.0), and up to 1mM hydrogen peroxide. In keeping with its adaptation to cold habitats, some polyunsaturated fatty acids, such as stearidonic acid (18:4n-3), eicosatetraenoic acid (20:4n-3), and eicosapentaenoic acid (20:5n-3), are produced at a higher level at low temperature. The genome is 4,456kb in size and has a GC content of 41.12%. Uniquely, strain #4 possesses genes for sialic acid metabolism and utilizes N-acetyl neuraminic acid as a carbon source. Interestingly, it also encodes for cytochrome c3 genes, which are known to facilitate environmental adaptation, including elevated temperatures and exposure to UV radiation. Phylogenetic analysis based on a consensus sequence of the seven 16S rRNA genes indicated that strain #4 belongs to genus Shewanella, closely associated with Shewanella aestuarii with a ~97% similarity, but with a low DNA–DNA hybridization (DDH) level of ~21%. However, average nucleotide identity (ANI) analysis defines strain #4 as a separate Shewanella species (ANI score=76). Further phylogenetic analysis based on the 92 most conserved genes places Shewanella strain #4 into a distinct phylogenetic clade with other cold-active marine Shewanella species. Considering the phylogenetic, phenotypic, and molecular characterization, we conclude that Shewanella strain #4 is a novel species and name it Shewanella glacialimarina sp. nov. TZS-4_T, where glacialimarina means sea ice. Consequently, S. glacialimarina TZS-4_T constitutes a promising model for studying transcriptional and translational regulation of cold-active metabolism.

Probiotic fermented oat dairy beverage: viability of Lactobacillus casei, fatty acid profile, phenolic compound content and acceptability

The combination of oats such as water-soluble oat extract (SOE) and probiotic microorganisms can add nutritional value to the food and benefits to the consumer's health. The SOE contains soluble fiber, whose major soluble fraction is composed of β-glucan contains soluble antioxidants such as ferulic acid, avenanthramides and other phenolic acids. The purpose of this study was to develop a fermented dairy beverage containing SOE, evaluating the viability of the probiotic culture, the fatty acid profile, phenolic compounds content and sensory characteristics during the storage. It was verified that Lactobacillus casei remained viable during the 21 days of storage (count above 7 Log CFU.mL^-1) and that the addition of SOE does not affect the viability of probiotic bacteria. The levels of bioactive compounds soluble in aqueous medium, increased between the beginning of the experiment and the end, being influenced by the addition of SOE. Seven fatty acids were found in all formulations with a prevalence of C16:0 followed by C18:1. The addition of SOE in the formulation contributes to a significant increase in linoleic acid (C18:2n6). The sensory evaluation of the fermented oat dairy beverage with L. casei (BAC) was positive: the product was highly appreciated by consumers, with acceptance rate of 84.4%. The combination of SOE, with L. casei in the production of novel probiotic fermented dairy beverage, was technologically feasible, improving the functional properties of the product and offering health benefits to the consumer. More studies should be made to evaluate the composition and functional properties of SOE.

Impact of Environment and Ontogeny on Relative Fecundity and Egg Quality of Female Oysters (Crassostrea virginica) from Four Sites in Northern Chesapeake Bay

Resource allocation to reproduction is a primary physiological concern for individuals, and can vary with age, environment, or a combination of both factors. In this study we quantified the impact of environment and individual age on the reproductive output of female oysters Crassostrea virginica. We determined the relative fecundity, egg total lipid content, and overall and omega-3/omega-6 (ω3/ω6) fatty acid signatures (FAS) of eggs spawned by female oysters over a 2-year period (n = 32 and n = 64). Variation was quantified spatially and ontogenetically by sampling young and old oyster populations from two rivers in Chesapeake Bay, totaling four collection sites. During Year 1, when oysters underwent oogenesis in different locations, overall and ω3/ω6 egg FAS varied significantly by river, with no significant differences observed in the FAS of oysters by age in Year 1. In Year 2, when oysters from different sites underwent oogenesis in a single location, no significant differences in the overall egg FAS or ω3/ω6 egg FAS by river or age were observed. These findings suggest that oysters integrate environment into their reproductive output, but that time spent growing at a specific location (in this case, represented by oyster age) plays a relatively minor role in the biochemical composition of oyster eggs. These results have consequences for our understanding of how resources are allocated from the female oyster to eggs and, more generally, the impact of environment and ontogeny on reproductive physiology.