Modeling and interpretation of bistatic bottom reverberation in deep water near seamounts.

The received reverberation signal can be beamformed by utilizing a vertical array, generating a vertical-angle time record (VATR) that enables analysis of spatiotemporal distribution characteristics. Due to the influence of multipath propagation effects, deep-sea reverberation exhibits highly complex characteristics, especially in a seabed with significant depth variation. In a recent bistatic reverberation experiment with a vertical array receiver, peculiar bright stripes were observed in the VATR. These stripes are the result of scattering caused by large-scale bottom structures and are closely associated with seamounts. To accurately model and interpret these stripes, a bistatic reverberation model is initially established to reproduce the VATR. This model enables us to numerically simulate the spatiotemporal distribution of reverberation in the VATR, offering a qualitative explanation for these stripes. However, the model alone is incapable of predicting the specific stripe structure associated with a particular seamount. To address this limitation, an equation system is introduced to calculate the stripe parameters based on the seamount parameters. By analyzing and deducing the dependency of the stripes on the seamount, conclusions were drawn using the equation system. Ultimately, the presented model and equation system successfully reproduce and comprehensively explain the observed abnormal stripes from the experiment.

Simultaneous Detection of Bladder Cancer Exosomal MicroRNAs Based on Inorganic Nanoflare and DNAzyme Walker.

Bladder cancer (BC) is one of the most common cancers in the world, with high morbidity and mortality. It is essential to develop a non-invasive, highly accurate, and simple method for BC diagnosis. This work proposed a fluorescent biosensor based on inorganic nanoflares combined with a DNAzyme walker for the simultaneous detection of BC exosomal microRNAs (miRNAs). This biosensor was constructed on the Au nanoparticle (AuNP) modified with the carbon dot (CD)-labeled substrates and DNAzyme strands (AuNP@CDs inorganic nanoflares-DNAzyme, APCD). In the presence of target miRNAs, DNAzyme was activated and then cleaved the CD-labeled substrates and automatically walked along the AuNP, allowing fluorescence recovery. Due to the structure and functional composition, the APCD biosensors demonstrated high sensitivity and specificity, with the reached limit of detection for a single miRNA at the femtomolar level and wide linear range from 50 fM to 10 nM. Furthermore, the simultaneous analysis of BC-related exosomal miR-133b and miR-135b in clinical serum specimens was achieved and consistent with qRT-PCR, suggesting it is a potential method for the diagnosis of BC and other cancers.

Fermentation parameters, antioxidant capacities, and volatile flavor compounds of tomato juice-skim milk mixtures fermented by Lactobacillus plantarum ST-III.

This study evaluated the influence of tomato juice enriched with the probiotic strain Lactobacillus plantarum ST-III on the flavor and health-promoting effects of fermented skim milk. Fermentation parameters, such as titratable acidity, viable cell counts, antioxidant activity, and volatile components, were examined. The viable bacterial cell counts of 40% tomato juice samples were significantly higher than those in the control group, peaking at 1.09 × 109 CFU/mL after 48 h, and the titratable acidity was increased by 2.76-fold versus the control value. The antioxidant ability of fermented milk was correlated with the tomato juice content in addition to fermentation time in the 2,2-diphenyl-1-picrylhydrazyl and ferric reducing/antioxidant power assays; for these methods, the scavenging activities of 40% samples were 1.18- and 1.28-fold higher than the control values, respectively, at 24 h. Moreover, abundant flavor components, especially aldehydes, were detected after the addition of L. plantarum ST-III-supplemented tomato juice.

Study on the Influence of Tea Extract on Probiotics in Skim Milk: From Probiotics Propagation to Metabolite.

In this study, the influence of tea extract (TE) on the growth of probiotics in skim milk was examined. Lactobacillus plantarum ST-III, Bifidobacterium bifidum Bb02, Lactobacillus acidophilus NCFM, and Lactobacillus rhamnosus GG were used in this study. The introduction of TE in milk significantly stimulated the propagation and acidification of L. rhamnosus GG and L. acidophilus NCFM. The antioxidant capacities and the total free amino acid contents of all fermented milk products were enhanced by the addition of TE; however, there were different antioxidant properties and free amino acid contents of fermented milk samples fermented by different bacteria. With a 9% (w/w) level, the fermentation with L. rhamnosus GG and L. acidophilus NCFM showed larger numbers of viable cells and faster acidifying rates, as well as excellent antioxidant capacity and abundant free amino acids.  The stimulative effects of TE on probiotics can be considered for industrial purposes and has practical implications for commercial applications.

Positive selection on D-lactate dehydrogenases of Lactobacillus delbrueckii subspecies bulgaricus.

Lactobacillus delbrueckii has been widely used for yogurt fermentation. It has genes encoding both D- and L-type lactate dehydrogenases (LDHs) that catalyse the production of L(+) or D(-) stereoisomer of lactic acid. D-lactic acid is the primary lactate product by L. delbrueckii, yet it cannot be metabolised by human intestine. Since it has been domesticated for long time, an interesting question arises regarding to whether the selection pressure has affected the evolution of both L-LDH and D-LDH genes in the genome. To answer this question, in this study the authors first investigated the evolution of these two genes by constructing phylogenetic trees. They found that D-LDH-based phylogenetic tree could better represent the phylogenetic relationship in the acidophilus complex than L-LDH-based tree. They next investigated the evolutions of LDH genes of L. delbrueckii at amino acid level, and found that D-LDH gene in L. delbrueckii is positively selected, possibly a consequence of long-term domestication. They further identified four amino acids that are under positive selection. One of them, V261, is located at the centre of three catalytic active sites, indicating likely functional effects on the enzyme activity. The selection from the domestication process thus provides direction for future engineering of D-LDH.

Cracking Streptococcus thermophilus to stimulate the growth of the probiotic Lactobacillus casei in co-culture.

Lactobacillus casei, a probiotic, and Streptococcus thermophilus, a fast acidifying lactic acid bacterial strain, are both used in the food industry. The aim of this study was to investigate the interaction between L. casei and S. thermophilus in the presence or absence of S. thermophilus-specific bacteriophage during milk fermentation. The acidification capability of L. casei co-cultured with S. thermophilus was significantly higher than that observed for L. casei or S. thermophilus cultured alone. However, the probiotic content (i.e., L. casei cell viability) was low. The fastest acidification and the highest viable L. casei cell count were observed in co-cultures of L. casei and S. thermophilus with S. thermophilus phage. In these co-cultures, S. thermophilus compensated for the slow acid production of L. casei in the early exponential growth phase. Thereafter, phage-induced lysis of the S. thermophilus cells eliminated the competition for nutrients, allowing L. casei to grow well. Additionally, the ruptured S. thermophilus cells released intracellular factors, which further promoted the growth and function of the probiotic bacteria. Crude cellular extract isolated from S. thermophilus also significantly accelerated the growth and propagation of L. casei, supporting the stimulatory role of the phage on this micro-ecosystem.