Conjugal transfer of plasmid pIP501 from Lactococcus lactis to Lactobacillus delbruckii subsp. bulgaricus and Lactobacillus helveticus

Abstract Plasmid pIP501 was transferred by conjugation from Lactococcus lactis to Lactobacillus delbrückii subsp. bulgaricus and Lactobacillus helveticus . Only Lb. delbrückii subsp. bulgaricus transconjugants could act as a donor in crosses with Lc. lactis . No Lactobacillus transconjugants were detected after inter- or intra-species Lactobacillus crosses. Plasmid pIP501 has undergone no detectable deletion or rearrangement during transfer from Lc. lactis to Lactobacillus strains.     

Brewers’ spent grain liquor as a feedstock for lactate production with Lactobacillus delbrueckii subsp. lactis

Brewers’ spent grain (BSG) is a low‐cost by‐product of the brewing process. BSG liquor names the liquid components of BSG, mainly glucose, maltose, and long‐chain α‐1,4‐glycosidic bond glucose oligomers. These substances should be separated in existing BSG biorefineries, as they might lead to an increased formation of microbe‐inhibiting compounds in well‐established hydrothermal/enzymatic saccharification processes. In most cases, this liquid fraction is discarded. The present study presents for the first time an optimized process with BSG liquor for the purpose of producing bulk chemicals (e.g., lactate) in relevant concentrations. The process comprises the application of yeast extract, produced from own brewing processes, as the sole supplemented complex constituent in a simultaneous fermentation and saccharification process. Kinetic parameters for the final optimized process conditions with the organism Lactobacillus delbrueckii subsp. lactis were: maximum specific growth rate µ_max  =  0.47 h^?1, maximum lactate concentration c_Lac, max  =  79.06 g L^?1, process yield Y_PS  =  0.89 g_Lac g_Sugar^?1, lactate production rate q_P  =  4.18 g_Lac g_CDW^?1 h^?1, and productivity P _15 h  =  4.93 g_Lac L^?1 h^?1. BSG liquor, linked with yeast extract from Brewers’ yeast, can be a promising substrate for further bioprocess engineering tasks and contribute to a holistic and sustainable usage of Brewers’ spent grain.     

Role of AIP56 disulphide bond and its reduction by cytosolic redox systems for efficient intoxication

Apoptosis‐inducing protein of 56 kDa (AIP56) is a major virulence factor of Photobacterium damselae subsp. piscicida, a gram‐negative pathogen that infects warm water fish species worldwide and causes serious economic losses in aquacultures. AIP56 is a single‐chain AB toxin composed by two domains connected by an unstructured linker peptide flanked by two cysteine residues that form a disulphide bond. The A domain comprises a zinc‐metalloprotease moiety that cleaves the NF‐kB p65, and the B domain is involved in binding and internalisation of the toxin into susceptible cells. Previous experiments suggested that disruption of AIP56 disulphide bond partially compromised toxicity, but conclusive evidences supporting the importance of that bond in intoxication were lacking. Here, we show that although the disulphide bond of AIP56 is dispensable for receptor recognition, endocytosis, and membrane interaction, it needs to be intact for efficient translocation of the toxin into the cytosol. We also show that the host cell thioredoxin reductase‐thioredoxin system is involved in AIP56 intoxication by reducing the disulphide bond of the toxin at the cytosol. The present study contributes to a better understanding of the molecular mechanisms operating during AIP56 intoxication and reveals common features shared with other AB toxins.     

Purification and kinetics of a protease-resistant,neutral, and thermostable phytase from Bacillus subtilis subsp. subtilis JJBS250 ameliorating food nutrition

Abstract

A novel protease-resistant and thermostable phytase from Bacillus subtilis subsp. subtilis JJBS250 was purified 36-fold to homogeneity with a combination of ammonium sulfate precipitation followed by Q-Sepharose and Sephadex G-50 chromatographic techniques. The estimated molecular mass of the purified phytase was 46?kDa by electrophoresis with optimal activity at pH 7.0 and 70?°C. About 19% of original activity was maintained at 80?°C for 10?min. Phytase activity was stimulated in presence of surfactants like Tween-20, Tween-80, and Triton X-100 and metal ions like Ca⁺², K⁺, and Co⁺² and it was inhibited by SDS and Mg⁺², Al⁺², and Fe⁺². Purified enzyme showed specificity to different salts of phytic acid and values of K_m and V_max were 0.293?mM and 11.49 nmoles s^?1, respectively for sodium phytate. The purified enzyme was resistant to proteases (trypsin and pepsin) that resulted in amelioration of food nutrition with simultaneous release of inorganic phosphate, reducing sugars, and soluble protein.     

A new subspecies of Pedicularis zeylanica (Scrophulariaceae) from the Western Ghats of south India

Pedicularis zeylanica subsp. anamallyensis T. Husain & A. Garg, a new subspecies of Nilgiri lousewort from the Western Ghats of south India, is described and illustrated.     

Characterization of bacteriocin bificin C6165: a novel bacteriocin

Aims

To purify and primarily characterize an anti‐Alicyclobacillus bacteriocin produced by Bifidobacterium animalis subsp. animalis CICC 6165, suggested to be named bificin C6165.

Methods and Results

During purification of the bificin C6165, optimal recovery was achieved with ammonium sulfate precipitation followed by two chromatographic steps. Mass spectrometry analyses revealed a distinctive peak corresponding to a molecular mass of 3395·1 Da. This bacteriocin was heat stable, effective after refrigerated storage and freeze–thaw cycles. The primary mode of action of bificin C6165 is most probably due to pore formation, as indicated by the efflux of K⁺ from metabolically active cells of Alicyclobacillus acidoterrestris. In the presence of 10 mmol l^?1 gadolinium, bificin C6165 did not affect cells of Alicyclobacillus acidoterrestris. This suggests that the mode of action of bificin C6165 relies on a net negatively charged cell surface.

Conclusions

Bificin C6165 is indeed a novel bacteriocin and it exhibited remarkable potency for Alicyclobacillus control.

Significance and Impact of the Study

Application of bacteriocins in preservation of fruit juices has seldom been studied. Bificin C6165 may be an alternative method to control juice spoilage by this Alicyclobacillus acidoterrestris and meet increasing consumer demand for nature and artificial chemical additive‐free food products.     

Monitoring resistance to Bacillus thuringiensis subsp. israelensis in the field by performing bioassays with each Cry toxin separately

Bacillus thuringiensis subsp. israelensis (Bti) is increasingly used worldwide for mosquito control and is the only larvicide used in the French Rhône-Alpes region since decades. The artificial selection of mosquitoes with field-persistent Bti collected in breeding sites from this region led to a moderate level of resistance to Bti, but to relatively high levels of resistance to individual Bti Cry toxins. Based on this observation, we developed a bioassay procedure using each Bti Cry toxin separately to detect cryptic Bti-resistance evolving in field mosquito populations. Although no resistance to Bti was detected in none of the three mosquito species tested (Aedes rusticus, Aedes sticticus and Aedes vexans), an increased tolerance to Cry4Aa (3.5-fold) and Cry11Aa toxins (8-fold) was found in one Ae. sticticus population compared to other populations of the same species, suggesting that resistance to Bti may be arising in this population. This study confirms previous works showing a lack of Bti resistance in field mosquito populations treated for decades with this bioinsecticide. It also provides a first panorama of their susceptibility status to individual Bti Cry toxins. In combination with bioassays with Bti, bioassays with separate Cry toxins allow a more sensitive monitoring of Bti-resistance in the field.     

High‐density molecular characterization and association mapping in Ethiopian durum wheat landraces reveals high diversity and potential for wheat breeding

Durum wheat (Triticum turgidum subsp. durum) is a key crop worldwide, and yet, its improvement and adaptation to emerging environmental threats is made difficult by the limited amount of allelic variation included in its elite pool. New allelic diversity may provide novel loci to international crop breeding through quantitative trait loci (QTL) mapping in unexplored material. Here, we report the extensive molecular and phenotypic characterization of hundreds of Ethiopian durum wheat landraces and several Ethiopian improved lines. We test 81 587 markers scoring 30 155 single nucleotide polymorphisms and use them to survey the diversity, structure, and genome‐specific variation in the panel. We show the uniqueness of Ethiopian germplasm using a siding collection of Mediterranean durum wheat accessions. We phenotype the Ethiopian panel for ten agronomic traits in two highly diversified Ethiopian environments for two consecutive years and use this information to conduct a genome‐wide association study. We identify several loci underpinning agronomic traits of interest, both confirming loci already reported and describing new promising genomic regions. These loci may be efficiently targeted with molecular markers already available to conduct marker‐assisted selection in Ethiopian and international wheat. We show that Ethiopian durum wheat represents an important and mostly unexplored source of durum wheat diversity. The panel analysed in this study allows the accumulation of QTL mapping experiments, providing the initial step for a quantitative, methodical exploitation of untapped diversity in producing a better wheat.