Enhancement of Acid Tolerance in Zymomonas mobilis by a Proton-Buffering Peptide

PURPOSE We conducted a study to evaluate the tolerance to and biologic effects of all-trans retinoic acid in patients with myelodysplastic syndrome. PATIENTS AND METHODS Thirty-nine patients with myelodysplastic syndrome were treated with oral all-trans retinoic acid for 6 weeks. Dose levels were 10, 25, 50, 100, 150, 200, and 250 mg/m2/d. At least three patients were treated on each dose level. RESULTS The most common side effects were mucocutaneous dryness and erythema, and hypertriglyceridemia. Dose-limiting side effects were diverse and included dermatitic problems, sensorineural hearing loss, headaches, nausea and vomiting, myalgias, and dyspnea. The maximum-tolerated dose was 150 mg/m2/d. Only one response was seen among 29 patients considered assessable for response. CONCLUSION All-trans retinoic acid can be safely administered to patients at doses up to 150 mg/m2/d for 6 weeks. However, as administered in this study, this compound does not appear to have significant activity in myelodysplastic syndromes.

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Effect οf οxygen availability and pH οn adaptive acid tolerance response of immobilized Listeria monocytogenes in structured growth media

Food Microbiology ◽

10.1016/j.fm.2021.103826 ◽

2021 ◽

Vol 99 ◽

pp. 103826

Author(s):

Ifigeneia P. Makariti ◽

Nikos C. Grivokostopoulos ◽

Panagiotis N. Skandamis

Keyword(s):

Listeria Monocytogenes ◽

Acid Tolerance ◽

Growth Media ◽

Acid Tolerance Response ◽

Tolerance Response

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A Novel Microbial Zearalenone Transformation through Phosphorylation

Toxins ◽

10.3390/toxins13050294 ◽

2021 ◽

Vol 13 (5) ◽

pp. 294

Author(s):

Yan Zhu ◽

Pascal Drouin ◽

Dion Lepp ◽

Xiu-Zhen Li ◽

Honghui Zhu ◽

...

Keyword(s):

Microbial Transformation ◽

Acid Tolerance ◽

Transformation Product ◽

The United States ◽

Corn Silage ◽

Rrna Gene ◽

Bacillus Spp ◽

High Concentrations ◽

The 16S Rrna Gene ◽

Bacillus Strains

Zearalenone (ZEA) is a mycotoxin widely occurring in many agricultural commodities. In this study, a purified bacterial isolate, Bacillus sp. S62-W, obtained from one of 104 corn silage samples from various silos located in the United States, exhibited activity to transform the mycotoxin ZEA. A novel microbial transformation product, ZEA-14-phosphate, was detected, purified, and identified by HPLC, LC-MS, and NMR analyses. The isolate has been identified as belonging to the genus Bacillus according to phylogenetic analysis of the 16S rRNA gene and whole genome alignments. The isolate showed high efficacy in transforming ZEA to ZEA-14-phosphate (100% transformation within 24 h) and possessed advantages of acid tolerance (work at pH = 4.0), working under a broad range of temperatures (22–42 °C), and a capability of transforming ZEA at high concentrations (up to 200 µg/mL). In addition, 23 Bacillus strains of various species were tested for their ZEA phosphorylation activity. Thirteen of the Bacillus strains showed phosphorylation functionality at an efficacy of between 20.3% and 99.4% after 24 h incubation, suggesting the metabolism pathway is widely conserved in Bacillus spp. This study established a new transformation system for potential application of controlling ZEA although the metabolism and toxicity of ZEA-14-phosphate requires further investigation.

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The Quorum Sensing Auto-Inducer 2 (AI-2) Stimulates Nitrogen Fixation and Favors Ethanol Production over Biomass Accumulation in Zymomonas mobilis

International Journal of Molecular Sciences ◽

10.3390/ijms22115628 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5628

Author(s):

Valquíria Campos Alencar ◽

Juliana de Fátima dos Santos Silva ◽

Renata Ozelami Vilas Boas ◽

Vinícius Manganaro Farnézio ◽

Yara N. L. F. de Maria ◽

...

Keyword(s):

Nitrogen Fixation ◽

Quorum Sensing ◽

Ethanol Production ◽

N2 Fixation ◽

Energy Demand ◽

Zymomonas Mobilis ◽

Biomass Accumulation ◽

High Energy ◽

Gram Negative ◽

Expression Of Genes

Autoinducer 2 (or AI-2) is one of the molecules used by bacteria to trigger the Quorum Sensing (QS) response, which activates expression of genes involved in a series of alternative mechanisms, when cells reach high population densities (including bioluminescence, motility, biofilm formation, stress resistance, and production of public goods, or pathogenicity factors, among others). Contrary to most autoinducers, AI-2 can induce QS responses in both Gram-negative and Gram-positive bacteria, and has been suggested to constitute a trans-specific system of bacterial communication, capable of affecting even bacteria that cannot produce this autoinducer. In this work, we demonstrate that the ethanologenic Gram-negative bacterium Zymomonas mobilis (a non-AI-2 producer) responds to exogenous AI-2 by modulating expression of genes involved in mechanisms typically associated with QS in other bacteria, such as motility, DNA repair, and nitrogen fixation. Interestingly, the metabolism of AI-2-induced Z. mobilis cells seems to favor ethanol production over biomass accumulation, probably as an adaptation to the high-energy demand of N2 fixation. This opens the possibility of employing AI-2 during the industrial production of second-generation ethanol, as a way to boost N2 fixation by these bacteria, which could reduce costs associated with the use of nitrogen-based fertilizers, without compromising ethanol production in industrial plants.

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