Summary The ability of a yeast cell to propagate [PSI+], the prion form of the Sup35 protein, is dependent on the molecular chaperone Hsp104. Inhibition of Hsp104 function in yeast cells leads to a failure to generate new propagons, the molecular entities necessary for [PSI+] propagation in dividing cells and they get diluted out as cells multiply. Over‐expression of Hsp104 also leads to [PSI+] prion loss and this has been assumed to arise from the complete disaggregation of the Sup35 prion polymers. However, in conditions of Hsp104 over‐expression in [PSI+] cells we find no release of monomers from Sup35 polymers, no monomerization of aggregated Sup35 which is not accounted for by the proportion of prion‐free [psi‐] cells present, no change in the molecular weight of Sup35‐containing SDS‐resistant polymers and no significant decrease in average propagon numbers in the population as a whole. Furthermore, they show that over‐expression of Hsp104 does not interfere with the incorporation of newly synthesised Sup35 into polymers, nor with the multiplication of propagons following their depletion in numbers while growing in the presence of guanidine hydrochloride. Rather, they present evidence that over‐expression of Hsp104 causes malpartition of [PSI+] propagons between mother and daughter cells in a sub‐population of cells during cell division thereby generating prion‐free [psi−] cells.

The continued propagation of the yeast [PSI(+)] prion requires the molecular chaperone Hsp104 yet in cells engineered to overexpress Hsp104; prion propagation is impaired leading to the rapid appearance of prion-free [psi(-)] cells. The underlying mechanism of prion loss in such cells is unknown but is assumed to be due to the complete dissolution of the prion aggregates by the ATP-dependent disaggregase activity of this chaperone. To further explore the mechanism, we have sought to identify cellular factors required for prion loss in such cells. Sti1p and Cpr7p are co-chaperones that modulate the activity of Hsp70/Ssa and Hsp90 chaperones and bind to the C-terminus of Hsp104. Neither Sti1p nor Cpr7p is necessary for prion propagation but we show that deletion of the STI1 and CPR7 genes leads to a significant reduction in the generation of [psi(-)] cells by Hsp104 overexpression. Deletion of the STI1 and CPR7 genes does not modify the elimination of [PSI(+)] by guanidine hydrochloride, which inhibits the ATPase activity of Hsp104 but does block elimination of [PSI(+)] by overexpression of either an ATPase-defective mutant of Hsp104 (hsp104(K218T/K620T)) or a 'trap' mutant Hsp104 (hsp104(E285Q/E687Q)) that can bind its substrate but can not release it. These results provide support for the hypothesis that [PSI(+)] elimination by Hsp104 overexpression is not simply a consequence of complete dissolution of the prion aggregates but rather is through a mechanism distinct from the remodelling activity of Hsp104.

In this study, we examined the association between antimicrobial resistance, CRISPR/Cas systems and virulence with phage susceptibility in Acinetobacter baumannii and investigated draft genomes of phage susceptible multidrug resistant A. baumannii strains from Thailand. We investigated 230 A. baumannii strains using 17 lytic A. baumannii phages and the phage susceptibility was 46.5% (107/230). Phage susceptibility was also associated with resistance to numerous antibiotics (p-value < 0.05). We also found association between biofilm formation and the presence of ompA gene among phage susceptible A. baumannii strains (p-value < 0.05). A. baumannii isolates carrying cas5 or combinations of two or three other cas genes, showed a significant increase in phage resistance. Whole-genome sequences of seven phage susceptible A. baumannii isolates revealed that six groups of antibiotic resistance genes were carried by all seven phage susceptible A. baumannii. All strains carried biofilm associated genes and two strains harbored complete prophages, acquired copper tolerance genes, and CRISPR-associated (cas) genes. In conclusion, our data exhibits an association between virulence determinants and biofilm formation among phage susceptible A. baumannii strains. These data help to understand the bacterial co-evolution with phages.

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Nowadays, most people are more concerned with their personal health. Salads that are ready to eat are frequently a healthy eating option. It is consumed raw and unheated, which promotes the growth of numerous microorganisms. Furthermore, microbial contamination may occur because of the use of contaminated water for cleaning and packing. Aeromonas spp. are bacteria that grow on the water’s surface. They can survive in water that has been chlorinated to eliminate bacteria, which is critical for public health. Because bacteria can produce and secrete a variety of enzymes that are toxic to human tissue, there are a number of factors that contribute to violence. In people with low immunity, the majority of them can cause serious disease. As a result, the goal of this research is to look into and identify Aeromonas spp. isolated from ready-to-eat salad. The 16s rDNA gene was used to confirm the findings, and a PCR was used to look into the virulence factor genes. In this study, 9 isolates of Aeromonas spp. were found in 136 ready-to-eat salad samples, accounting for 6.6 percent of the total. Six virulence genes (ast, fla, lip, act, alt, and aphB) were used to identify each of 9 isolates where fla were found 4 isolates (44.44 %), and ahpB were also discovered 8 isolates (88.88 %). Therefore, there is the potential that ready to eat salad can be contaminated by Aeromonas spp. containing virulence factor which can cause a severe health risk such as diarrhea to consumers.