Pre-cold stress increases acid stress resistance and induces amino acid homeostasis in Lactococcus lactis NZ9000

Purpose: To investigate the effects of pre-cold stress treatments on subsequent acid stress resistance and the viability of Lactococcus lactis during acid fermentation.Methods: Bacterial strains were grown at 4 °C for 2 h pre-adaptation, and then subjected to various stresses including exposure to 4 °C, 1 mM hydrogen peroxide, 5 % sodium chloride, 7 % ethanol, and lactic acid (pH 5.5) to determine if any of these stress treatments could increase acid stress resistance and induce amino acid homeostasis during acid fermentation.Results: Among the different abiotic stresses investigated, pre-adaptation of lag-phase cultures to cold shock significantly enhanced cell survival during subsequent acid stress. The stress profile of L. lactis pre-adapted to cold stress revealed induction of amino acid homeostasis and energy balance; however, pre-adaptation responses are induced upon exposure to acid stress alone. Compared to exposure to acid stress only, pre-adaptation to cold stress decreased the redox balance ratio and the formation of hydroxyl radicals, indicating a change in aerobic respiration and oxidative state of the bacteria.Conclusion: Pre-adaptation to cold stress rescued L. lactis from the deleterious effects of subsequent acid exposure by modifying the amino acid metabolic pathway, leading to an improvement in redox mobility of acid stress response.Keywords: Pre-cold stress, Acis stress resistance, Lactococcus lactis, Redox balance, Amino acid homeostasi

Introduction of the flora, life form and chorology of the Parrotia persica C.A. Mey. Habitats (case study: Izdeh-e Noor area)

The lowland Caspian habitats are remnant (relict) patches of deciduous Euro-Siberian forests distributed in the Iranian three Northern provinces. Izdeh-e Noor plain forest with 3123 hectors is one of the great patches. In spite of a few studies, broad knowledge upon the flora and biodiversity of these areas does not exist. A total of 157 species belonging to 137 genera and 67 plant families were collected from the Parrotia persica habitats in the plain forest. The largest families in terms of species richness, were Poaceae (17 spp.), Rosaceae (13 spp.), Asteraceae, Fabaceae, Lamiaceae (each with 6 spp.), respectively. The genera with the largest number of species were Carex (4 spp.) and Rubus, Viola (each with 3 spp.), respectively. In the assessment of life form spectrum, the dominant life forms were geophytes (36.9%), followed by the phanerophytes (24.2%), hemicryptophytes (21.7%) and therophytes (17.2%). The flora was mostly composed of Euro-Siberian elements with 45 taxa (28.7%), followed by pluriregional elements with 32 taxa (20.4%), Euro-Siberian/Irano-Turanian/Mediterranean elements with 31 taxa (19.7%) and Euro-Siberian/Irano-Turanian elements with 27 taxa (17.2%). Among taxa collected from this area, 51 taxa (32.5%) in forest habitats, 54 taxa (34.4%) in margin and gap of forest and 52 taxa (33.1%) are present in both habitats