Three novel leaderless bacteriocins have antimicrobial activity against gram-positive bacteria to serve as promising food biopreservative.

BACKGROUND: Due to the detrimental effects of chemical preservatives, there has been an increasing demand for safer, healthier and natural bio-preservatives. Bacteriocins have attracted increasing interest because of their potential as natural bio-preservatives. RESULTS: We screened a large number of Bacillus thuringiensis strains and isolated one strain (B. thuringiensis P86) with antimicrobial activity against several foodborne pathogens. Three novel leaderless bacteriocins, including thucin A1, thucin A2 and thucin A3, were purified and identified from the culture supernatant of B. thuringiensis P86, whose molecular masses were 5552.02, 5578.07 and 5609.06 Da, respectively. Thucin A1 was then selected as a representative to be tested, and it exhibited potent inhibitory activity against all tested gram-positive bacteria. More importantly, thucin A1 showed stronger antimicrobial activity than nisin A against two important foodborne pathogens Bacillus cereus and Listeria monocytogenes. In addition, thucin A1 exhibited strong acid-base adaptability (pH 2-11), high endurance to heat, good stability to trypsin and pepsin, no hemolysis activity and cytotoxicity, and could effectively inhibit or eliminate Bacillus cereus and Listeria monocytogenes in skim milk. CONCLUSIONS: Our findings indicate that these novel leaderless bacteriocins are potentially promising food biopreservatives.

Koliella bifissiva sp. nov (Chlorellaceae, Chlorophyta) and Analysis of Its Organelle Genomes.

Chlorellacean members are common in aquatic or subaerial habitats, and many of them have significant economic value. Taxonomic reports and organelle genome data for the Nannochloris clade, an important subgroup within this family, are limited, hindering the understanding and exploitation of this clade. In this study, a fusiform-celled strain, FACHB-3607, was isolated from a pond in China. Through examination of morphological characteristics and phylogenetic analyses of rbcL, 18S rDNA, and ITS, it was identified as a new species within the Nannochloris clade, named Koliella bifissiva sp. nov. In addition, this study provided a first insight into the organellar genomes of the genus Koliella. The K. bifissiva chloroplast had a 99.8 kb genome, and the mitochondrion had a 40.8 kb genome, which are moderate sizes within the Nannochloris clade. Phylogenomic analysis showed that K. bifissiva is most closely related to Nannochloris sp. "desiccata", followed by Marvania. In contrast, Picochlorum was the most distantly related species. The organelle genomes of the Nannochloris clade display dynamic evolution, reflected in variations in genome size, gene content and order, and selection pressure. This research enhances our knowledge of species diversity and evolutionary history in the Nannochloris clade.

Root-knot nematodes exploit the catalase-like effector to manipulate plant reactive oxygen species levels by directly degrading H2O2.

Plants produce reactive oxygen species (ROS) upon infection, which typically trigger defence mechanisms and impede pathogen proliferation. Root-knot nematodes (RKNs, Meloidogyne spp.) represent highly detrimental pathogens capable of parasitizing a broad spectrum of crops, resulting in substantial annual agricultural losses. The involvement of ROS in RKN parasitism is well acknowledged. In this study, we identified a novel effector from Meloidogyne incognita, named CATLe, that contains a conserved catalase domain, exhibiting potential functions in regulating host ROS levels. Phylogenetic analysis revealed that CATLe is conserved across RKNs. Temporal and spatial expression assays showed that the CATLe gene was specifically up-regulated at the early infection stages and accumulated in the subventral oesophageal gland cells of M. incognita. Immunolocalization demonstrated that CATLe was secreted into the giant cells of the host plant during M. incognita parasitism. Transient expression of CATLe significantly dampened the flg22-induced ROS production in Nicotiana benthamiana. In planta assays confirmed that M. incognita can exploit CATLe to manipulate host ROS levels by directly degrading H2O2. Additionally, interfering with expression of the CATLe gene through double-stranded RNA soaking and host-induced gene silencing significantly attenuated M. incognita parasitism, highlighting the important role of CATLe. Taken together, our results suggest that RKNs can directly degrade ROS products using a functional catalase, thereby manipulating host ROS levels and facilitating parasitism.

Unzipped chromosome-level genomes reveal allopolyploid nematode origin pattern as unreduced gamete hybridization.

The formation and consequences of polyploidization in animals with clonal reproduction remain largely unknown. Clade I root-knot nematodes (RKNs), characterized by parthenogenesis and allopolyploidy, show a widespread geographical distribution and extensive agricultural destruction. Here, we generated 4 unzipped polyploid RKN genomes and identified a putative novel alternative telomeric element. Then we reconstructed 4 chromosome-level assemblies and resolved their genome structures as AAB for triploid and AABB for tetraploid. The phylogeny of subgenomes revealed polyploid RKN origin patterns as hybridization between haploid and unreduced gametes. We also observed extensive chromosomal fusions and homologous gene expression decrease after polyploidization, which might offset the disadvantages of clonal reproduction and increase fitness in polyploid RKNs. Our results reveal a rare pathway of polyploidization in parthenogenic polyploid animals and provide a large number of high-precision genetic resources that could be used for RKN prevention and control.

Comparative Genomics of Exiguobacterium Reveals What Makes a Cosmopolitan Bacterium.

Although the strategies used by bacteria to adapt to specific environmental conditions are widely reported, fewer studies have addressed how microbes with a cosmopolitan distribution can survive in diverse ecosystems. Exiguobacterium is a versatile genus whose members are commonly found in various habitats. To better understand the mechanisms underlying the universality of Exiguobacterium, we collected 105 strains from diverse environments and performed large-scale metabolic and adaptive ability tests. We found that most Exiguobacterium members have the capacity to survive under wide ranges of temperature, salinity, and pH. According to phylogenetic and average nucleotide identity analyses, we identified 27 putative species and classified two genetic groups: groups I and II. Comparative genomic analysis revealed that the Exiguobacterium members utilize a variety of complex polysaccharides and proteins to support survival in diverse environments and also employ a number of chaperonins and transporters for this purpose. We observed that the group I species can be found in more diverse terrestrial environments and have a larger genome size than the group II species. Our analyses revealed that the expansion of transporter families drove genomic expansion in group I strains, and we identified 25 transporter families, many of which are involved in the transport of important substrates and resistance to environmental stresses and are enriched in group I strains. This study provides important insights into both the overall general genetic basis for the cosmopolitan distribution of a bacterial genus and the evolutionary and adaptive strategies of Exiguobacterium. IMPORTANCE The wide distribution characteristics of Exiguobacterium make it a valuable model for studying the adaptive strategies of bacteria that can survive in multiple habitats. In this study, we reveal that members of the Exiguobacterium genus have a cosmopolitan distribution and share an extensive adaptability that enables them to survive in various environments. The capacities shared by Exiguobacterium members, such as their diverse means of polysaccharide utilization and environmental-stress resistance, provide an important basis for their cosmopolitan distribution. Furthermore, the selective expansion of transporter families has been a main driving force for genomic evolution in Exiguobacterium. Our findings improve our understanding of the adaptive and evolutionary mechanisms of cosmopolitan bacteria and the vital genomic traits that can facilitate niche adaptation.

De novo transcriptome sequencing and analysis revealed the molecular basis of rapid fat accumulation by black soldier fly (Hermetia illucens, L.) for development of insectival biodiesel.

BACKGROUND: Black soldier fly (BSF, Hermetia illucens L.) can efficiently degrade organic wastes and transform into a high fat containing insect biomass that could be used as feedstock for biodiesel production. Meanwhile, the molecular regulatory basis of fat accumulation by BSF is still unclear; it is necessary to identify vital genes and regulators that are involved in fat accumulation. RESULTS: This study analyzed the dynamic state of fat content and fatty-acid composition of BSF larvae in eight different stages. The late prepupa stage exhibited the highest crude fat, with lauric acid being the main component. Therefore, to provide insight into this unexplained phenomenon, the molecular regulation of rapid fat accumulation by BSF larvae was investigated. The twelve developmental stages of BSF were selected for transcriptome analysis, including the eight stages used for investigation of fat content and fatty-acid composition. By Illumina sequencing, 218,295,450,000 nt were generated. Through assembly by Trinity, 70,475 unigenes were obtained with an average length of 1064 nt and an N50 of 1749 nt. The differentially expressed unigenes were identified by DESeq, with 9159 of them being up-regulated and 10,101 of them were down-regulated. The several putative genes that are involved in the formation of pyruvate, acetyl-CoA biosynthesis, acetyl-CoA transcription, fatty-acid biosynthesis, and triacylglycerol biosynthesis were identified. The four vital metabolic genes that are associated with fat accumulation were validated by quantitative real-time PCR (qRT-PCR). The molecular mechanism of fat accumulation in BSF was clarified in this investigation through the construction of a detailed fat accumulation model from our results. CONCLUSION: The study provides an unprecedented level of insight from transcriptome sequencing to reveal the crude fat accumulation mechanism in developing BSF. The finding holds considerable promise for insectival biodiesel production, and the fat content and fatty-acid composition can be altered by genetic engineering approaches in the future for the insect production industry.

Development and comparison of intramuscularly long-acting paliperidone palmitate nanosuspensions with different particle size.

The main purpose of this study was to develop and compare the pharmacokinetic behavior of two paliperidone palmitate (PP) nanosuspensions with different particle size after intramuscular (i.m.) administration. PP nanosuspensions were prepared by wet media milling method and the mean particle size of nanosuspension was controlled as 1,041 ± 6 nm (A) and 505 ± 9 nm (B), respectively. The morphology of nanosuspensions was observed by scanning electron microscope (SEM). Differential scanning calorimeter (DSC) and powder X-ray diffraction (PXRD) confirmed the crystallinity of PP in nanosuspensions. The physical and chemical stabilities of nanosuspensions A and B were investigated by particle analyzer and HPLC after storage for 2 months at 25°C, 4°C and mechanical shaking condition. No obvious change in particle size and chemical degradation of drug were observed. Following single-dose i.m. administration to beagle dogs, the release of paliperidone lasted for nearly 1 month. The Tmax of nanosuspensions A and B was 6 (d) and 10 (d). The AUC0-t and Cmax of nanosuspensions A was 2.0-fold and 1.8-fold higher than nanosuspensions B (p<0.05). The results demonstrated that PP nanosuspensions formulation had long-acting effect. Nanosuspension A with a larger particle size performed better than nanosuspension B. As a result, it is important to design appropriate particle size of nanosuspensions for i.m. administration in order to produce larger therapeutic effect.