A novel quadrant spatial assay reveals environmental preference in mouse spontaneous and parental behaviors.

Environmental factors have well-documented impacts on brain development and mental health. Therefore, it is crucial to employ a reliable assay system to assess the spatial preference of model animals. In this study, we introduced an unbiased quadrant chamber assay system and discovered that parental pup-gathering behavior takes place in a very efficient manner. Furthermore, we found that test mice exhibited preferences for specific environments in both spontaneous and parental pup-gathering behavior contexts. Notably, the spatial preferences of autism spectrum disorder model animals were initially suppressed but later equalized during the spontaneous behavior assay, accompanied by increased time spent in the preferred chamber. In conclusion, our novel quadrant chamber assay system provides an ideal platform for investigating the spatial preference of mice, offering potential applications in studying environmental impacts and exploring neurodevelopmental and psychiatric disorder models.

New role of a histone chaperone, HirA: Involvement in kojic acid production associated with culture conditions in Aspergillusoryzae.

Kojic acid (KA) is a representative secondary metabolite of Aspergillus oryzae, but the underlying molecular mechanisms that regulate KA production are unknown. This study tried to find a genetic factor of KA production in A. oryzae, with a special focus on liquid cultures. We screened a gene predicted to encode HirA, a subunit of the histone chaperon, the HIR complex. A gene disruption strain of hirA showed decreased KA production in liquid culture, whereas it showed increased KA production in plate culture. We confirmed that a decrease/increase of KA production observed by hirA disruption was caused by altered expression of kojA and kojR. These observations suggested the regulatory role of histone chaperon in secondary metabolism in filamentous fungi. So far as we know, this report is the first showing that disruption of a gene resulted in the opposite effect on KA production in liquid and plate cultures in A. oryzae.

A unique Zn(II)2-Cys6-type protein, KpeA, is involved in secondary metabolism and conidiation in Aspergillus oryzae.

Aspergillus oryzae is an important microorganism in the bio- and food industries; therefore, understanding the mechanism underlying its secondary metabolism regulation is important for ensuring its safe use. Here, we screened a novel Zn(II)2-Cys6-type protein-encoding gene, AO090003001186, designated as kpeA (kojic acid production enhancement A), from an A. oryzae disruption mutant library of transcriptional regulators. kpeA is highly conserved among filamentous fungi and encodes a protein with Zn(II)2-Cys6 motif located in the middle of the sequence. Phylogenetic analysis revealed that KpeA was classified into a distal group compared to other fungal Zn(II)2-Cys6-type transcriptional regulators. A Cys to Ala substitution mutant of KpeA showed identical phenotype to the kpeA disruption strain, confirming that KpeA is novel type Zn(II)2-Cys6 binding protein. Colonies of the kpeA disruption strain (ΔkpeA) had longer aerial hyphae and showed decreased conidia production. Microscopic analysis suggested that the reduced vesicle size and conidial head formation in ΔkpeA strain account for the decreased conidia production. Transcriptional levels of brlA and downstream abaA and wetA were decreased in ΔkpeA strain. Moreover, ΔkpeA strain produced 6-fold more kojic acid than the control strains, and the expression of kojR and kojA was increased in ΔkpeA strain. Therefore, KpeA is a novel Zn(II)2-Cys6-type protein likely involved in conidiation and kojic acid production at the transcriptional level.

In vitro antimicrobial activity of aminoreductone against the pathogenic bacteria methicillin-resistant Staphylococcus aureus (MRSA).

In this study, antimicrobial activity of aminoreductone (AR), a product formed during the initial stage of the Maillard reaction, against methicillin-resistant Staphylococcus aureus (MRSA) was evaluated. The significant growth inhibition of all 51 MRSA isolates irrespective of drug susceptibility by AR was observed. The minimum inhibitory concentration (MIC) of AR ranged from 13 to 26 mM. The bactericidal activity of AR was evaluated by a killing assay with multiples of MIC, and it was recognized to depend on its dose. The combined effects of AR and antibiotics frequently used for the treatment of infections caused by Gram-positive and Gram-negative bacteria, such as amikacin (AN), ciprofloxacin, imipenem and levofloxacin, were examined. As a result, AR did not interfere with these antibiotic activities against 12 MRSA isolates selected and showed the advanced effect of growth inhibition in combination with antibiotics. Moreover, the inhibitory effects of AR were similar to those of AN, an antibiotic with known adverse effects, some serious. These findings show that AR is a naturally formed antimicrobial agent present in thermally processed foods with potential health benefits in medical practice.

Antimicrobial activity of aminoreductone against Helicobacter pylori.

Anti-Helicobacter pylori (H. pylori) effects of aminoreductone (AR), a Maillard reaction product, were evaluated in this study. AR effectively inhibited the growth of all 24 strains (19 clinical isolates and 5 isogenic mutants) irrespective of susceptibility to antibiotics and clinical manifestation. The minimum inhibitory concentration (MIC) of AR ranged from 0.5 to 5 mM. A killing assay with multiples of MIC was performed, demonstrating that the killing activity of AR was significantly higher than that of its derived melanoidin, an inhibitor of H. pylori urease-gastric mucin adherence, formed in the final stage of the Maillard reaction. These significant effects of AR on H. pylori were observed even in acidic conditions (pH 3). At most, 25 mM AR effectively exhibited bactericidal activity in all strains. These results rise up the possibility that foods containing AR, such as milk and dairy products, are valuable sources for preventing colonization of H. pylori in the stomach and its associated tissue damages.