Search

Tilapia is one of most important foodfish species. The low omega-3 to omega-6 fatty acid ratio in freshwater tilapia meat is disadvantageous for human health. Increasing omega-3 content is an important task in breeding to increase the nutritional value of tilapia. However, conventional breeding to increase omega-3 content is difficult and slow. To accelerate the increase of omega-3 through marker-assisted selection (MAS), we conducted QTL mapping for fatty acid contents and profiles in a F2 family of saline tilapia generated by crossing red tilapia and Mozambique tilapia. The total omega-3 content in F2 hybrid tilapia was 2.5 ± 1.0 mg/g, higher than that (2.00 mg/g) in freshwater tilapia. Genotyping by sequencing (GBS) technology was used to discover and genotype SNP markers, and microsatellites were also genotyped. We constructed a linkage map with 784 markers (151 microsatellites and 633 SNPs). The linkage map was 2076.7 cM long and consisted of 22 linkage groups. Significant and suggestive QTL for total lipid content were mapped on six linkage groups (LG3, -4, -6, -8, -13, and -15) and explained 5.8–8.3% of the phenotypic variance. QTL for omega-3 fatty acids were located on four LGs (LG11, -18, -19, and -20) and explained 5.0 to 7.5% of the phenotypic variance. Our data suggest that the total lipid and omega-3 fatty acid content were determined by multiple genes in tilapia. The markers flanking the QTL for omega-3 fatty acids can be used in MAS to accelerate the genetic improvements of these traits in salt-tolerant tilapia. [ABSTRACT FROM AUTHOR]

ABSTRACT Biofilms are the most ubiquitous and resilient form of microbial life on earth. One most important feature of a biofilm is the presence of a self-produced matrix, which creates highly heterogeneous and dynamic microenvironments within biofilms. Redox status in biofilm microenvironments plays a critical role in biofilm development and function. However, there is a lack of non-intrusive tools to quantify extracellular redox status of microenvironments within a biofilm matrix. In this study, using Shewanella oneidensis as a model organism, we demonstrated a novel approach to monitor extracellular redox status in biofilm microenvironments. Specifically, we displayed a redox sensitive fluorescence protein roGFP onto the cell surface of S. oneidensis by fusing it to the C-terminus of BpfA, a large surface protein, and used the surface displayed roGFP as a sensor to quantify the extracellular redox status in the matrix of S. oneidensis biofilms. The fusion of roGFP into BpfA has no negative impacts on cell growth and biofilm formation. Upon exposure to oxidizing agents such as H2O2, Ag+, and SeO32−, S. oneidensis BpfA-roGFP cells exhibited a characteristic fluorescence of roGFP. Proteinase treatment assay and super-resolution structured illumination microscopy confirmed the surface localization of BpfA-roGFP. We further used the surface displayed roGFP monitored the extracellular redox status in the matrix at different depths of a biofilm exposed to H2O2. This study provides a novel approach to non-invasively monitor extracellular redox status in microenvironments within biofilms, which can be used to understand redox responses of biofilms to environmental perturbations. Biotechnol. Bioeng. 2015;112: 512-520. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The oleaginous yeast Rhodosporidium toruloides, which belongs to the Pucciniomycotina subphylum in the Basidiomycota, has attracted strong interest in the biofuel community recently due to its ability to accumulate more than 60% of dry biomass as lipid under high-density fermentation. A 3,543-nucleotide (nt) DNA fragment of the glyceraldehyde-3-phosphate dehydrogenase gene ( GPD1) was isolated from R. toruloides ATCC 10657 and characterized in details. The 1,038-nt mRNA derived from seven exons encodes an open reading frame (ORF) of 345 amino acids that shows high identity (80%) to the Ustilago maydis homolog. Notably, the ORF is composed of codons strongly biased towards cytosine at the Wobble position. GPD1 is transcriptionally regulated by temperature shock, osmotic stress, and carbon source. Nested deletion analysis of the GPD1 promoter by GFP reporter assay revealed that two regions, −975 to −1,270 and −1,270 to −1,429, upstream from the translational start site of GPD1 were important for responses to various stress stimuli. Interestingly, a 176-bp short fragment maintained 42.2% promoter activity of the 795-bp version in U. maydis whereas it was reduced to 17.4% in R. toruloides. The GPD1 promoter drove strong expression of a codon-optimized enhanced green fluorescent protein gene (Rt GFP) and a codon-optimized hygromycin phosphotransferase gene ( hpt-3), which was critical for Agrobacterium tumefaciens-mediated transformation in R. toruloides. [ABSTRACT FROM AUTHOR]

Aedes aegypti (Linnaeus, 1762) is the insect vector that transmits several deadly human diseases. Although the egg stage is an important phase of its life cycle, the biology of mosquito egg remains poorly understood. Here, we report our investigations on the chemical factors that induced hatching of Ae. aegypti eggs. Commercial yeast extracts were able to increase egg hatching rate in a dose-dependent manner, with a hatching rate that ranged from approximately 10% with 1 g/liter to 80% with 20 g/liter of yeast extract. Notably, the addition of glutathione, a reducing agent that showed no significant effect on egg hatching by itself, enhanced and stabilized the activity of yeast extract for at least 70 h. Because dissolved oxygen in different treatments was maintained at high levels in a narrow range (92-95%), we proposed that yeast extract contains hatching inducing compound (HIC) which is able to trigger egg hatching independent of dissolved oxygen level. The HIC in yeast extract could prove to be a potential starting point to design an effective tool to forcefully induce mosquito eggs to hatch under unfavorable conditions, functioning as a novel method for vector control., (© The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

A novel strain S29 T with high nitrogen fixing ability was isolated from surface-sterilized leaf tissues of oil palm ( Elaeis guineensis ) growing in Science Park II, Singapore. On the basis of 16S rRNA gene analysis and multilocus sequence typing with the rpoB, gyrB, infB and atpD genes, strain S29 T was a member of the genus Phytobacter , with Phytobacter ursingii ATCC 27989 T and Phytobacter diazotrophicus LS 8 T as its closest relatives. Unique biochemical features that differentiated strain S29 T from its closest relatives were the ability to utilize melibiose, α -cyclodextrin, glycogen, adonital, d-arabitol, m -inositol and xylitol. The major fatty acids were C 14 : 0 , C 16 : 0 , C 17 : 0 , C 16 : 1 ω 5c and summed feature 2 containing C 16 : 1 ω 7c and/or C 16 : 1 ω 6c. The polar fatty acid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminophospholipid and aminolipids. The draft genome of strain S29 T comprised 5, 284, 330 bp with a G + C content of 52.6 %. The average nucleotide identity and digital DNA-DNA hybridization values between strain S29 T and the phylogenetically related Enterobacterales species were lower than 95 % and 70 %, respectively. Thus, the polyphasic evidences generated through the phenotypic, chemotaxonomic and genomic methods confirmed that strain S29 T represents a novel species of the genus Phytobacter , for which we propose the name Phytobacter palmae sp. nov. with the type strain of S29 T (=DSM 27342 T =KACC 17598 T ).

Background: Rhodosporidium toruloides is a β-carotenoid accumulating, oleaginous yeast that has great biotechnological potential. The lack of reliable and efficient genetic manipulation tools have been a major hurdle blocking its adoption as a biotechnology platform., Results: We report for the first time the development of a highly efficient targeted gene deletion method in R. toruloides ATCC 10657 via Agrobacterium tumefaciens-mediated transformation. To further improve targeting frequency, the KU70 and KU80 homologs in R. toruloides were isolated and characterized in detail. A KU70-deficient mutant (∆ku70e) generated with the hygromycin selection cassette removed by the Cre-loxP recombination system showed a dramatically improved targeted gene deletion frequency, with over 90% of the transformants being true knockouts when homology sequence length of at least 1 kb was used. Successful gene targeting could be made with homologous flanking sequences as short as 100 bp in the ∆ku70e strain. KU70 deficiency did not perturb cell growth although an elevated sensitivity to DNA mutagenic agents was observed. Compared to the other well-known oleaginous yeast, Yarrowia lipolytica, R. toruloides KU70/KU80 genes contain much higher density of introns and are the most GC-rich KU70/KU80 genes reported., Conclusions: The KU70-deficient mutant generated herein was effective in improving gene deletion frequency and allowed shorter homology sequences to be used for gene targeting. It retained the key oleaginous and fast growing features of R. toruloides. The strain should facilitate both fundamental and applied studies in this important yeast, with the approaches taken here likely to be applicable in other species in subphylum Pucciniomycotina.