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Hormesis, or the hormetic effect, is a dose- or concentration-dependent response characterised by growth stimulation at low concentrations and inhibition at high concentrations. The impact of sub-lethal levels of disinfectants on the growth of Serratia species is critical to understanding the increasing number of outbreaks caused by this pathogen in healthcare settings. Serratia sp. HRI and Serratia marcescens ATCC 13880 were cultivated in sub-lethal levels of benzalkonium chloride (BAC), Didecyldimethylammonium chloride (DDAC), and VirukillTM. The maximum specific growth rates, doubling times, and cell counts were compared. The results revealed significant increases in maximum specific growth rates and shorter doubling times for Serratia sp. HRI when cultivated in sub-lethal levels of BAC and DDAC. The significant stimulatory effect of sub-lethal levels of these disinfectants for Serratia sp. HRI represents the first time hormesis has been observed in a Gram-negative bacterium for any disinfectant. Furthermore, this study is the first to observe the hormetic effect after treatment with DDAC and the second study to date analysing the impact of sub-lethal levels of disinfectants on the growth of bacterial species. [ABSTRACT FROM AUTHOR]

Sesotho is an indigenous cereal-based fermented drink traditionally produced in the mountain kingdom of Lesotho, Southern Africa. The present study sought to examine the microbial (bacterial and fungal) community composition of Sesotho at five fermentation stages in five different locations. Using culture-independent (Illumina sequencing) techniques it was found that the bacterial communities followed similar successional patterns during the fermentation processes, regardless of geographical location and recipe variation between breweries. The most abundant bacterial taxa belonged to the phyla Firmicutes (66.2% of the reads on average) and Proteobacteria (22.1%); the families Lactobacillaceae (54.9%), Enterobacteriaceae (14.4%) and Leoconostrocaceae (8.1%); and the genera Lactobacillus (54%), Leuconostoc (10.7%), Leptotrichia (8.5%), and Weissella (5.5%). Most fungal taxa were from the phyla Ascomycota (60.7%) and Mucoromycota (25.3%); the families Rhizopodaceae (25.3%), Nectriaceae (24.2%), Saccharomycetaceae (16%) and Aspergillaceae (6.7%); and the genera Rhizopus (25.3%), Saccharomyces (9.6%), and Aspergillus (2.5%). Lactic acid bacteria (LAB) such as Enterococcus , Pediococcus , Lactobacillus , Leuconostoc , and Wiesella ; as well as yeasts belonging to the genus Saccharomyces , were dominant in all breweries during the production of Sesotho. Several pathogenic and food spoilage microorganisms (e.g., Escherichia , Shigella , Klebsiella , etc.) were also present, but the study demonstrated the safety potential of the Sesotho fermentation process, as these microbial groups decline throughout Sesotho production. The functional profiles of the different brewing steps showed that the process is dominated by chemoheterotrophic and fermentative metabolisms. This study reveals, for the first time, the complex microbial dynamics that occur during Sesotho production. [ABSTRACT FROM AUTHOR]

We investigated the transcriptomic response of a new strain of the yeast Kluyveromyces marxianus, in glucose and xylose media using RNA-seq. The data were explored in a number of innovative ways using a variety of networks types, pathway maps, enrichment statistics, reporter metabolites and a flux simulation model, revealing different aspects of the genome-scale response in an integrative systems biology manner. The importance of the subcellular localisation in the transcriptomic response is emphasised here, revealing new insights. As was previously reported by others using a rich medium, we show that peroxisomal fatty acid catabolism was dramatically up-regulated in a defined xylose mineral medium without fatty acids, along with mechanisms to activate fatty acids and transfer products of β-oxidation to the mitochondria. Notably, we observed a strong up-regulation of the 2-methylcitrate pathway, supporting capacity for odd-chain fatty acid catabolism. Next we asked which pathways would respond to the additional requirement for NADPH for xylose utilisation, and rationalised the unexpected results using simulations with Flux Balance Analysis. On a fundamental level, we investigated the contribution of the hierarchical and metabolic regulation levels to the regulation of metabolic fluxes. Metabolic regulation analysis suggested that genetic level regulation plays a major role in regulating metabolic fluxes in adaptation to xylose, even for the high capacity reactions, which is unexpected. In addition, isozyme switching may play an important role in re-routing of metabolic fluxes in subcellular compartments in K. marxianus. [ABSTRACT FROM AUTHOR]

BACKGROUND The cladodes of Opuntia ficus-indica (prickly pear cactus) have a low protein content; for use as a balanced feed, supplementation with other protein sources is therefore desirable. We investigated protein enrichment by cultivation of the yeasts Candida utilis and Kluyveromyces marxianus in an enzymatic hydrolysate of the cladode biomass. RESULTS Dilute acid pretreatment and enzymatic hydrolysis of sun-dried cladodes resulted in a hydrolysate containing (per litre) 45.5 g glucose, 6.3 g xylose, 9.1 g galactose, 10.8 g arabinose and 9.6 g fructose. Even though K. marxianus had a much higher growth rate and utilized l-arabinose and d-galactose more completely than C. utilis, its biomass yield coefficient was lower due to ethanol and ethyl acetate production despite aerobic cultivation. Yeast cultivation more than doubled the protein content of the hydrolysate, with an essential amino acid profile superior to sorghum and millet grains. CONCLUSIONS This K. marxianus strain was weakly Crabtree positive. Despite its low biomass yield, its performance compared well with C. utilis. This is the first report showing that the protein content and quality of O. ficus-indica cladode biomass could substantially be improved by yeast cultivation, including a comparative evaluation of C. utilis and K. marxianus. © 2014 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The lipolytic activity, lipid oxidation, sensory effect and production of volatile compounds by Chryseobacterium joostei and Pseudomonas fluorescens in full cream milk, incubated at 4 and 25 °C, were investigated. Lipolytic activity, measured by the amount of free fatty acids released, showed high levels for both organisms. Although no significant differences between C. joostei and Ps. fluorescens were observed at 4 °C, C. joostei was significantly ( P < 0.001) more lipolytic than Ps. fluorescens at 25 °C. Lipid oxidation was measured by thiobarbituric acid analysis. No significant differences between any of the inoculated milk samples were noted. During sensory analysis, C. joostei produced stronger odours than Ps. fluorescens . Different odours were also described for the two species. Volatile compound analysis determined that C. joostei has the ability to produce the same amount of off-odours during psychrotrophic and mesophilic growth conditions as Ps. fluorescens , but with different odour profiles. [ABSTRACT FROM AUTHOR]

A Gram-stain-negative, rod-shaped, non-motile, non-spore-forming, aerobic, yellow-pigmented bacterium was isolated from chicken feather waste collected from an abattoir in Bloemfontein, South Africa. A polyphasic taxonomy study was used to describe and name the bacterial isolate, strain 1&#95;F178 T . The 16S rRNA gene sequence analysis and sequence comparison data indicated that strain 1&#95;F178 T was a member of the genus Chryseobacterium and was closely related to Chryseobacterium jejuense (99.1%) and Chryseobacterium nakagawai (98.7%). Overall genome similarity metrics (average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity) revealed greatest similarity to the C. jejuense and C. nakagawai type strains but were below the threshold for species delineation. Genome sequencing revealed a genome size of 6.18 Mbp and a G+C content of 35.6 mol%. The major respiratory quinone and most abundant polar lipid of strain 1&#95;F178 T were menaquinone-6 and phosphatidylethanolamine, respectively. Strain 1&#95;F178 T had a typical fatty acid composition for Chryseobacterium species. On the basis of physiological, genotypic, phylogenetic and chemotaxonomic data, strain 1&#95;F178 T constitutes a novel species of Chryseobacterium , for which the name Chryseobacterium pennae sp. nov. is proposed. The type strain is 1&#95;F178 T (=LMG 30779 T =KCTC 62759 T ).

Strain 7&#95;F195 T was previously isolated from chicken feather waste collected from an abattoir in Bloemfontein, South Africa. A polyphasic approach was followed to determine if strain 7&#95;F195 T belongs to the genus Chryseobacterium and if the organism can be classified as a new species. The nearest neighbours, based on 16S rRNA gene sequence similarity values (indicated in parentheses), were Chryseobacterium flavum KCTC 12877 T (98.42 %), Chryseobacterium indologenesLMG 8337 T (98.24 %) and Chryseobacterium gleum ATCC 35910 T (97.71 %). Genome sequencing revealed a genome size of 4 796 535 bp and a DNA G+C content of 38.6 mol%. The ANI values of strain 7&#95;F195 T compared to C. flavum, C. indologenesand C. gleum were 81.45, 81.86 and 82.38 %, respectively. The digital DNA-DNA hybridization values for strain 7&#95;F195 T with C. flavum, C. indologenes and C. gleum were 23.7, 23.7 and 24.9 %, respectively. Notable phenotypic differences include the presence of urease activity in C. indologenes LMG 8337 T and C. gleum NCTC 11432 T , but not in strain 7&#95;F195 T or C. flavum KCTC 12877 T . The predominant fatty acids of strain 7&#95;F195 T were iso-C15 : 0, iso-C17 : 1ω9c and iso-C17 : 0 3-OH and the most abundant polar lipid was phosphatidylethanolamine. Menaquinone-6 was the only respiratory quinone. Based on the data generated from this polyphasic study, strain 7&#95;F195 T represents a novel Chryseobacterium species for which the name Chryseobacteriumpennipullorum sp. nov. is proposed. The type strain is 7&#95;F195 T (=LMG 30781 T =KCTC 62760 T ).