A Novel Non-Coding RNA CsiR Regulates the Ciprofloxacin Resistance in Proteus vulgaris by Interacting with emrB mRNA

A Point Mutation in Cassette Relieves the Repression Regulation of CcpA Resulting in an Increase in the Degradation of 2,3-Butanediol in Lactococcus lactis

In lactic acid bacteria, the global transcriptional regulator CcpA regulates carbon metabolism by repressing and activating the central carbon metabolism pathway, thus decreasing or increasing the yield of certain metabolites to maximize carbon flow. However, there are no reports on the deregulation of the inhibitory effects of CcpA on the metabolism of secondary metabolites. In this study, we identified a single-base mutant strain of Lactococcus lactis N8-2 that is capable of metabolizing 2,3-butanediol. It has been established that CcpA dissociates from the catabolite responsive element (cre) site due to a mutation, leading to the activation of derepression and expression of the 2,3-butanediol dehydrogenase gene cluster (butB and butA). Transcriptome analysis and quantitative polymerase chain reaction (Q-PCR) results showed significant upregulation of transcription of butB and butA compared to the unmutated strain. Furthermore, micro-scale thermophoresis experiments confirmed that CcpA did not bind to the mutated cre. Furthermore, in a bacterial two-plasmid fluorescent hybridization system, it was similarly confirmed that the dissociation of CcpA from cre eliminated the repressive effect of CcpA on downstream genes. Finally, we investigated the differing catalytic capacities of the 2,3-butanediol dehydrogenase gene cluster in L. lactis N8-1 and L. lactis N8-2 for 2,3-butanediol. This led to increased expression of butB and butA, which were deregulated by CcpA repression. This is the first report on the elimination of the deterrent effect of CcpA in lactic acid bacteria, which changes the direction of enzymatic catalysis and alters the direction of carbon metabolism. This provides new perspectives and strategies for metabolizing 2,3-butanediol using bacteria in synthetic biology.

Bullfrogs (Lithobates catesbeianus) as a Potential Source of Foodborne Disease

In Mexico, bullfrogs (Lithobates catesbeianus) are produced as gourmet food. However, bullfrogs can be carriers of pathogens because the frogs' preferred living conditions occur in stagnant water. The present study aimed to identify bacteria that cause foodborne diseases or are associated with human diseases. For molecular identification, based on the sequential analysis by 16S rRNA or rpoD was conducted on all isolates obtained from bullfrog. A total of 91 bacterial isolates were obtained from bullfrogs; 14 genera and 23 species were identified, including Acinetobacter johnsonii 16.5%; Aeromonas media 14.3%; Aeromonas veronii 13.2%; Providencia rettgeri 7.7%; Citrobacter freundii 6.6%; Aeromonas caviae 4.4%; Aeromonas hydrophila and Elizabethkingia ursingii 3.3%; Pseudomonas stutzeri, Raoultella ornithinolytica, and Shewanella putrefaciens 2.2%; Acinetobacter guillouiae, Acinetobacter pseudolwoffii, Citrobacter portucalensis, Citrobacter werkmanii, Edwardsiella anguillarum, Klebsiella michiganensis, Kluyvera intermedia, Kocuria rosea, Myroides odoratimimus, Myroides odoratus, Proteus sp., and Proteus hauseri 1.1%. In this study, 49.4% of the isolates obtained cause foodborne disease, 19.8% are bacteria that play an important role in the spoilage of food, 5.5% of isolates have nosocomial significance, 13.2% of bacteria are considered to be pollutants of the ecosystem, and in the case of A. salmonicida and Edwardsiella anguillarum (12.1%) to have a negative impact on aquaculture. Acinetobacter pseudolwoffii and Citrobacter portucalensis have not been reported to cause disease. Lastly of these isolates, 97.8% (89/91) can cause disease by food consumption or by direct contact for immunocompromised persons. The presence of these bacteria in bullfrogs represents a significant problem for human health. There is evidence that these microorganisms are pathogenic and frogs may also be reservoirs.

Anti-virulence therapeutic strategies against bacterial infections: recent advances

The emergence and increasing prevalence of multidrug-resistant pathogens has become a major global healthcare problem. According to the World Health Organization if these trends continue, mortality from infection in 2050 will be higher than that from cancer. Microorganisms have various resistance mechanisms against different classes of antibiotics that emphasize the need for discovery of new antimicrobial compounds to treat bacterial infections. An interesting and new strategy for disarming pathogens is antivirulence therapy by blocking bacterial virulence factors or pathogenicity. Therefore, the use of these new pathoblockers could reduce the administration of broad-spectrum antimicrobials and prevalence of resistant strains. This review provides an overview of the antivirulence strategies published studies between years 2017 and 2021. Most antivirulence strategies focused on adhesins, toxins and bacterial communication. Additionally, targeting two-component systems and ncRNA elements were also examined in some studies. These new strategies have the potential to replace traditional antimicrobial agents and can be used to treat infections, especially infections caused by resistant pathogens, by targeting virulence factors.

Targeting the Holy Triangle of Quorum Sensing, Biofilm Formation, and Antibiotic Resistance in Pathogenic Bacteria

Chronic and recurrent bacterial infections are frequently associated with the formation of biofilms on biotic or abiotic materials that are composed of mono- or multi-species cultures of bacteria/fungi embedded in an extracellular matrix produced by the microorganisms. Biofilm formation is, among others, regulated by quorum sensing (QS) which is an interbacterial communication system usually composed of two-component systems (TCSs) of secreted autoinducer compounds that activate signal transduction pathways through interaction with their respective receptors. Embedded in the biofilms, the bacteria are protected from environmental stress stimuli, and they often show reduced responses to antibiotics, making it difficult to eradicate the bacterial infection. Besides reduced penetration of antibiotics through the intricate structure of the biofilms, the sessile biofilm-embedded bacteria show reduced metabolic activity making them intrinsically less sensitive to antibiotics. Moreover, they frequently express elevated levels of efflux pumps that extrude antibiotics, thereby reducing their intracellular levels. Some efflux pumps are involved in the secretion of QS compounds and biofilm-related materials, besides being important for removing toxic substances from the bacteria. Some efflux pump inhibitors (EPIs) have been shown to both prevent biofilm formation and sensitize the bacteria to antibiotics, suggesting a relationship between these processes. Additionally, QS inhibitors or quenchers may affect antibiotic susceptibility. Thus, targeting elements that regulate QS and biofilm formation might be a promising approach to combat antibiotic-resistant biofilm-related bacterial infections.