CRISPR-Cas9 mediated adiA knockout in Hafnia paralvei: Implications for agmatine production and acid stress survival in a fermented dairy matrix.
CRISPR-Cas9 knockout of adiA in Hafnia paralvei reveals its critical role in agmatine production and acid stress survival, with potential implications for functional food development.
Where it sits
this study against the rest of the vasopressin corpusSummary and findings
The study used CRISPR-Cas9 to knockout the adiA gene in Hafnia paralvei to assess its role in agmatine production and acid stress survival. Agmatine accumulation was observed under acidic conditions, and the adiA gene was identified as essential for this process. The knockout confirmed adiA's role in acid stress resistance.
Abstract
Agmatine, the product of the decarboxylation of arginine, catalysed by arginine decarboxylase (ADC), is a bioactive compound that functions as a neuromodulator and co-transmitter and has gained increasing attention in recent years due to its therapeutic potential, particularly for its neuroprotective properties. Members of the genus Hafnia are the main agmatine producers in dairy products. In this regard, Hafnia is considered a beneficial microorganism due to its ability to enhance cheese organoleptic properties and its emerging probiotic potential, making it relevant for functional food development, specially agmatine-enriched dairy products. This study aimed to identify the genetic basis for agmatine production in Hafnia paralvei and to assess its role in bacterial fitness. Genomic analysis of the strain H. paralvei IPLA15029 revealed the presence of two genes encoding putative ADC enzymes, adiA and speA, however, organized slightly different than those in other enterobacteria. In some bacteria, ADC exists in two forms: one involved in polyamine biosynthesis, encoded by the constitutive speA gene, and another involved in acid stress resistance, encoded by the adiA gene, which is inducible under acidic conditions. In vivo experiments under controlled pH conditions showed that agmatine accumulation occurs exclusively under acidic conditions, which also stabilize the compound by preventing its catabolism to putrescine. Gene expression analysis revealed that adiA was transcribed as a monocistronic unit, and that in these conditions, adiA is the gene responsible for agmatine production. This was confirmed by generating an adiA knockout mutant after the implementation of the CRISPR-Cas9 system, marking the first successful application of this technology in the genus Hafnia. Moreover, the adiA knockout demonstrated that the encoded arginine decarboxylase is essential for survival under severe acid stress.
Background
The study investigates the genetic basis of agmatine production in Hafnia paralvei, a bacterium known for its role in enhancing the organoleptic properties of cheese and its potential as a probiotic. Agmatine, a neuromodulator and co-transmitter, has gained attention for its therapeutic potential, particularly in neuroprotection. Understanding the genetic mechanisms behind its production could inform the development of functional foods enriched with agmatine.
Methods
The study employed CRISPR-Cas9 technology to knockout the adiA gene in Hafnia paralvei IPLA15029. Genomic analysis identified two genes, adiA and speA, encoding putative arginine decarboxylase enzymes. In vivo experiments were conducted under controlled pH conditions to assess agmatine production and bacterial fitness. Gene expression analysis was performed to determine the transcriptional organization of adiA.
Results
The primary finding was that agmatine accumulation in Hafnia paralvei occurs exclusively under acidic conditions, with adiA being the key gene responsible for its production. The adiA knockout mutant confirmed the gene's essential role in acid stress resistance, as the mutant showed impaired survival under severe acid stress. This study marked the first successful use of CRISPR-Cas9 in the genus Hafnia.
Interpretation
The study provides insights into the genetic regulation of agmatine production in Hafnia paralvei, highlighting the role of adiA in acid stress survival. While the findings are significant for understanding bacterial adaptation and potential probiotic applications, the clinical relevance remains limited due to the in vitro nature of the study. The use of CRISPR-Cas9 in Hafnia opens avenues for further genetic studies in this genus.
Key findings
- CRISPR-Cas9 successfully knocked out the adiA gene in Hafnia paralvei.
- Agmatine accumulation occurs exclusively under acidic conditions.
- adiA is transcribed as a monocistronic unit responsible for agmatine production.
- adiA knockout mutant showed impaired survival under severe acid stress.
- First successful application of CRISPR-Cas9 in the genus Hafnia.
Limitations
- In vitro study with Hafnia paralvei only.
- Findings may not translate to in vivo conditions.
- Single bacterial strain studied.
- No direct clinical relevance established.