Escherichia coli strains defective in the rpiA gene, encoding ribose phosphate isomerase A, are ribose auxotrophs, despite the presence of the wild-type rpiB gene, which encodes ribose phosphate isomerase B. Ribose prototrophs of an rpiA genetic background were isolated by two different approaches. Firstly, spontaneous ribose-independent mutants were isolated. The locus for this lesion, rpiR, was mapped to 93 min on the linkage map, and the gene order zje::Tn10-rpiR-mel-zjd::Tn10-psd-purA was established. Secondly, ribose prototrophs resulted from the cloning of the rpiB gene on a multicopy plasmid. The rpiB gene resided on a 4.6-kbp HindIII-EcoRV DNA fragment from phage 10H5(642) of the Kohara gene library and mapped at 92.85 min. Consistent with this map position, the cloned DNA fragment contained two divergent open reading frames of 149 and 296 codons, encoding ribose phosphate isomerase B (molecular mass, 16,063 Da) and a negative regulator of rpiB gene expression, RpiR (molecular mass, 32,341 Da), respectively. The 5 ends of rpiB-and rpiR-specified transcripts were located by primer extension analysis. No significant amino acid sequence similarity was found between ribose phosphate isomerases A and B, but ribose phosphate isomerase B exhibited high-level similarity to both LacA and LacB subunits of the galactose 6-phosphate isomerases of several gram-positive bacteria. Analyses of strains containing rpiA, rpiB, or rpiA rpiB mutations revealed that both enzymes were equally efficient in catalyzing the isomerization step in either direction and that the construction of rpiA rpiB double mutants was a necessity to fully prevent this reaction.

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Highlights We present the first WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. Globally in 2016, 488 million people were exposed to long working hours (≥55 hours/week). This exposure had 745,194 attributable deaths and 23.3 million DALYs from ischemic heart disease and stroke. These are 4.9% of all deaths and 6.9% of all DALYs from these causes. The Western Pacific, South-East Asia, men, and older people carried higher burdens.

The food industry is constantly striving to develop new products to fulfil the ever changing demands of consumers and the strict requirements of regulatory agencies. For foods based on microbial fermentation, this pushes the boundaries of microbial performance and requires the constant development of new starter cultures with novel properties. Since the use of ingredients in the food industry is tightly regulated and under close scrutiny by consumers, the use of recombinant DNA technology to improve microbial performance is currently not an option. As a result, the focus for improving strains for microbial fermentation is on classical strain improvement methods. Here we review the use of these techniques to improve the functionality of lactic acid bacteria starter cultures for application in industrial-scale food production. Methods will be described for improving the bacteriophage resistance of specific strains, improving their texture forming ability, increasing their tolerance to stress and modulating both the amount and identity of acids produced during fermentation. In addition, approaches to eliminating undesirable properties will be described. Techniques include random mutagenesis, directed evolution and dominant selection schemes.

cBacillus spp. are widely used as feed additives and probiotics. However, there is limited information on their resistance to various antibiotics, and there is a growing concern over the transfer of antibiotic resistance genes. The MIC for 8 antibiotics was determined for 85 Bacillus species strains, Bacillus subtilis subsp. subtilis (n ‫؍‬ 29), Bacillus licheniformis (n ‫؍‬ 38), and Bacillus sonorensis (n ‫؍‬ 18), all of which were isolated from starters for Sudanese bread production. All the strains were sensitive to tetracycline (

The induction of the heat shock response in Lactococcus lactis subsp. cremoris strain MG1363 was analysed at the RNA level using a novel RNA isolation procedure to prevent degradation. Cloning of the dnal and gm€L homologues was carried out. Northern blot analysis showed a similar induction pattern for dnaK, dnal and gm€LS after transfer from 30 "C to 43 "C when MG1363 was grown in defined medium. The dnaK gene showed a 100-fold induction level 15 min after temperature shifting. Induction of the first two genes in the dnaK operon, off7 and g @ , resembled the pattern observed for the above genes, although maximum induction was observed earlier for off7 and grlpE. Novel transcript sizes were detected in heat-shocked cells. The induction kinetics observed for fcsH suggested a different regulation for this gene. Experimental evidence for a pronounced transcriptional regulation being involved in the heat shock response in L. lactis MG1363 is presented. A gene located downstream of the dnaK operon in strain MG1363, named odd, was shown not to be regulated by heat shock.

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