Observations on Neritina turrita (Gmelin 1791) Breeding Behaviour in Laboratory Conditions

Neritina turrita (Gmelin 1791) along with other Neritina, Clithon, Septaria, and other fresh-water snails are popular animals in ornamental aquarium trade. The need for laboratory-bred animals, eliminating the potential biohazard risks, for the ornamental aquarium trade and the growing demand for animal model systems for biomedical research reasons the work for optimising a successful breading protocol. The initial results demonstrate N. turrita as tough animals, surviving fluctuations in pH from 5 to 9, and shifts from a fresh-water environment to brackish (2 - 20 ppt), to sea-water (35 ppt) salinities. The females laid over 630 (at salinities 0, 2, 10 ppt and temperatures of 25 - 28oC) white oval 1 by 0.5 mm egg capsules continuously within 2 months after collecting semen from several males. Depositions of egg capsules are set apart 6 +/-3 days, and consist on average of 53(range 3 to 192) egg capsules. Production of viable veligers was recorded under laboratory conditions. Keywords: Neritina turrita, Sea-water, Temperatures, Environment

Updated Taxonomy of Pectobacterium genus in the CIRM-CFBP Bacterial Collection: When Newly Described Species Reveal “Old” Endemic Population

Bacterial collections are invaluable tools for microbiologists. However, their practical use is compromised by imprecise taxonomical assignation of bacterial strains. This is particularly true for soft rotting plant pathogens of the Pectobacterium genus. To solve this difficulty, we analyzed the taxonomic status of 265 Pectobacterium strains deposited at CIRM-CFBP collection from 1944 to 2020. This collection gathered Pectobacterium strains isolated in 27 countries from 32 plant species representing 17 botanical families or from non-host environments. MLSA approach completed by genomic analysis of 15 strains was performed to update the taxonomic status of these 265 strains. Results showed that the CIRM-CFBP Pectobacterium collection harboured at least one strain of each species to the exception of P. polonicum. Yet, 6 strains could not be assigned to any of the described species and may represent at least two new species. Surprisingly, the P. versatile species, recently described in 2019, is the most prevalent species among CIRM-CFBP strains. Analysis of P. versatile strains revealed that this species is endemic all over the world on various host plants and environments. At the opposite, other species gathered strains isolated from only one botanical family or exclusively from fresh water environment. Our work also revealed new host plants for several Pectobacterium spp.

Biodiversity of new lytic bacteriophages infecting Shigella spp. in fresh water environment

Background Bacteriophages, viruses that infects and replicates within prokaryotic cells are the most abundant life forms in the environment, yet the vast majority of them have not been properly reported or even discovered. Almost all reported bacteriophages infecting the Enterobacteriaceae family, with E. coli being the major subject of the study, have been isolated from wastewater, sewage, and effluent resources. In the present study we focused on the distribution and biodiversity of Shigella phages in an aquatic ecosystem. Results While no Shigella bacteria was recovered from the Yangtze River, three lytic phages were isolated from this ecosystem and were subjected to biological, morphological, and genomic characteristics. Comparative genomics and phylogenetic analyses demonstrated that vB _SflM_004 isolate belongs to Myoviridae family, Felixounavirus genus of Ounavirinae subfamily, vB_SdyM_006 was classified under the same family, however, it is suggested to be in a new genus under Tevenvirinae subfamily with some other related bacteriophages. vB_SsoS_008 phage belongs to the Siphoviridae family, Tunavirus genus, Tunavirinae subfamily. The phages did not harbor any genes involved in the lysogenic cycles, and showed a high temperature and pH stability. Conclusions It can be concluded that isolation of bacteriophages could be independent of their bacterial host presence in the isolation environment.

Application of mathematical tools and techniques in monitoring and predicting stainless steel corrosion in river water media environment

The application of mathematical tools and techniques were applied in the process of monitoring and predicting the corrosion rate and weight loss of stainless steel in salt and fresh water environment of Niger Delta region in Nigeria. The functional parameters used in the mathematical demonstration to compute the corrosion rate and weight loss were obtained from the experimental data and these functional coefficients were fitted into the power and quadratic model. The experimental corrosion rate and weight loss value was compared with the theoretical computed value for both model of quadratic and power concept approach and the result obtained demonstrate a good match indicating the reliability of the concepts on monitoring and predicting the process. In this case, the corrosion rate and weight loss was experienced to be more rapid in the salt water environment than the fresh water environment; this can be attributed to the characteristics of the salt water concentration of the physicochemical parameters that is a major contributing factor for increase in corrosion rate and weight of metals in aqueous media.

The influence of spanwise confinement on round fountains

We study experimentally the effects of spanwise confinement on turbulent miscible fountains issuing from a round source of radius $r_{0}$. A dense saline solution is ejected vertically upwards into a fresh-water environment between two parallel plates, separated by a gap of width $W$, which provide restraint in the spanwise direction. The resulting fountain, if sufficiently forced, rapidly attaches to the side plates as it rises and is therefore ‘confined’. We report on experiments for five confinement ratios $W/r_{0}$, spanning from strongly confined ($W/r_{0}\rightarrow 2$) to weakly confined ($W/r_{0}\approx 24$), and for source Froude numbers $Fr_{0}$ ranging between $0.5\leqslant Fr_{0}\leqslant 96$. Four distinct flow regimes are observed across which the relative importance of confinement, as manifested by the formation and growth of quasi-two-dimensional structures, varies. The onset of each regime is established as a function of both $W/r_{0}$ and $Fr_{0}$. From our analysis of the time-averaged rise heights, we introduce a ‘confined’ Froude number $Fr_{c}\equiv Fr_{0}(W/r_{0})^{-5/4}$, which encompasses the effects of confinement and acts as the governing parameter for confined fountains. First-order statistics extracted from the flow visualisation, such as the time-averaged rise height and lateral excursions, lend further insight into the flow and support the proposed classification into regimes. For highly confined fountains, the flow becomes quasi-two-dimensional and, akin to quasi-two-dimensional jets and plumes, flaps (or meanders). The characteristic frequency of this flapping motion, identified through an ‘eddy counting’ approach, is non-dimensionalised to a Strouhal number of $St=0.12{-}0.16$, consistent with frequencies found in quasi-two-dimensional jets and plumes.