Carbon dioxide requirement of Neisseria gonorrhoeae growing on a solid medium

Neisseria gonorrhoeae carbonic anhydrase inhibition

Carbonic anhydrases (CAs) are ubiquitous enzymes that are found in all kingdoms of life. Though different classes of CAs vary in their roles and structures, their primary function is to catalyze the reaction between carbon dioxide and water to produce bicarbonate and a proton. Neisseria gonorrhoeae encodes for three distinct CAs (NgCAs) from three different families: an α-, a β-, and a γ-isoform. This chapter details the differences between the three NgCAs, summarizing their subcellular locations, roles, essentiality, structures, and enzyme kinetics. These bacterial enzymes have the potential to be drug targets; thus, previous studies have investigated the inhibition of NgCAs-primarily the α-isoform. Therefore, the classes of inhibitors that have been shown to bind to the NgCAs will be discussed as well. These classes include traditional CA inhibitors, such as sulfonamides, phenols, and coumarins, as well as non-traditional inhibitors including anions and thiocarbamates.

Dinner date: Neisseria gonorrhoeae central carbon metabolism and pathogenesis

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhea, is a human-adapted pathogen that does not productively infect other organisms. The ongoing relationship between N. gonorrhoeae and the human host is facilitated by the exchange of nutrient resources that allow for N. gonorrhoeae growth in the human genital tract. What N. gonorrhoeae 'eats' and the pathways used to consume these nutrients have been a topic of investigation over the last 50 years. More recent investigations are uncovering the impact of N. gonorrhoeae metabolism on infection and inflammatory responses, the environmental influences driving N. gonorrhoeae metabolism, and the metabolic adaptations enabling antimicrobial resistance. This mini-review is an introduction to the field of N. gonorrhoeae central carbon metabolism in the context of pathogenesis. It summarizes the foundational work used to characterize N. gonorrhoeae central metabolic pathways and the effects of these pathways on disease outcomes, and highlights some of the most recent advances and themes under current investigation. This review ends with a brief description of the current outlook and technologies under development to increase understanding of how the pathogenic potential of N. gonorrhoeae is enabled by metabolic adaptation.

CanB is a metabolic mediator of antibiotic resistance in Neisseria gonorrhoeae

The evolution of the obligate human pathogen Neisseria gonorrhoeae has been shaped by selective pressures from diverse host niche environments and antibiotics. The varying prevalence of antibiotic resistance across N. gonorrhoeae lineages suggests that underlying metabolic differences may influence the likelihood of acquisition of specific resistance mutations. We hypothesized that the requirement for supplemental CO₂, present in approximately half of isolates, reflects one such example of metabolic variation. Here, using a genome-wide association study and experimental investigations, we show that CO₂ dependence is attributable to a single substitution in a β-carbonic anhydrase, CanB. CanB^19E is necessary and sufficient for growth in the absence of CO₂, and the hypomorphic CanB^19G variant confers CO₂ dependence. Furthermore, ciprofloxacin resistance is correlated with CanB^19G in clinical isolates, and the presence of CanB^19G increases the likelihood of acquisition of ciprofloxacin resistance. Together, our results suggest that metabolic variation has affected the acquisition of fluoroquinolone resistance.

PrintrLab incubator: A portable and low-cost CO2 incubator based on an open-source 3D printer architecture

Growth in open-source hardware designs combined with the decreasing cost of high-quality 3D printers have supported a resurgence of in-house custom lab equipment development. Herein, we describe a low-cost (< $400), open-source CO2 incubator. The system is comprised of a Raspberry Pi computer connected to a 3D printer controller board that has controls for a CO2 sensor, solenoid valve, heater, and thermistors. CO2 is supplied through the sublimation of dry ice stored inside a thermos to create a sustained 5% CO2 supply. The unit is controlled via G-Code commands sent by the Raspberry Pi to the controller board. In addition, we built a custom software application for remote control and used the open-source Grafana dashboard for remote monitoring. Our data show that we can maintain consistent CO2 and temperature levels for over three days without manual interruption. The results from our culture plates and real-time PCR indicate that our incubator performed equally well when compared to a much more expensive commercial CO2 incubator. We have also demonstrated that the antibiotic susceptibility assay can be performed in this low-cost CO2 incubator. Our work also indicates that the system can be connected to incubator chambers of various chamber volumes.

Metal-Limited Growth of Neisseria gonorrhoeae for Characterization of Metal-Responsive Genes and Metal Acquisition from Host Ligands

Trace metals such as iron and zinc are vital nutrients known to play key roles in prokaryotic processes including gene regulation, catalysis, and protein structure. Metal sequestration by hosts often leads to metal limitation for the bacterium. This limitation induces bacterial gene expression whose protein products allow bacteria to overcome their metal-limited environment. Characterization of such genes is challenging. Bacteria must be grown in meticulously prepared media that allows sufficient access to nutritional metals to permit bacterial growth while maintaining a metal profile conducive to achieving expression of the aforementioned genes. As such, a delicate balance must be established for the concentrations of these metals. Growing a nutritionally fastidious organism such as Neisseria gonorrhoeae, which has evolved to survive only in the human host, adds an additional level of complexity. Here, we describe the preparation of a defined metal-limited medium sufficient to allow gonococcal growth and the desired gene expression. This method allows the investigator to chelate iron and zinc from undesired sources while supplementing the media with defined sources of iron or zinc, whose preparation is also described. Finally, we outline three experiments that utilize this media to help characterize the protein products of metal-regulated gonococcal genes.

Neisseria gonorrhoeae host adaptation and pathogenesis

The host-adapted human pathogen Neisseria gonorrhoeae is the causative agent of gonorrhoea. Consistent with its proposed evolution from an ancestral commensal bacterium, N. gonorrhoeae has retained features that are common in commensals, but it has also developed unique features that are crucial to its pathogenesis. The continued worldwide incidence of gonorrhoeal infection, coupled with the rising resistance to antimicrobials and the difficulties in controlling the disease in developing countries, highlights the need to better understand the molecular basis of N. gonorrhoeae infection. This knowledge will facilitate disease prevention, surveillance and control, improve diagnostics and may help to facilitate the development of effective vaccines or new therapeutics. In this Review, we discuss sex-related symptomatic gonorrhoeal disease and provide an overview of the bacterial factors that are important for the different stages of pathogenesis, including transmission, colonization and immune evasion, and we discuss the problem of antibiotic resistance.

Biomineralization-based conversion of carbon dioxide to calcium carbonate using recombinant carbonic anhydrase

Recently, as a mimic of the natural biomineralization process, the use of carbonic anhydrase (CA), which is an enzyme catalyzing fast reversible hydration of carbon dioxide to bicarbonate, has been suggested for biological conversion of CO(2) to valuable chemicals. While purified bovine CA (BCA) has been used in previous studies, its practical utilization in CO(2) conversion has been limited due to the expense of BCA preparation. In the present work, we investigated conversion of CO(2) into calcium carbonate as a target carbonate mineral by using a more economical, recombinant CA. To our knowledge, this is the first report of the usage of recombinant CA for biological CO(2) conversion. Recombinant α-type CA originating in Neisseria gonorrhoeae (NCA) was highly expressed as a soluble form in Escherichia coli. We found that purified recombinant NCA which showed comparable CO(2) hydration activity to commercial BCA significantly promoted formation of solid CaCO(3) through the acceleration of CO(2) hydration rate, which is naturally slow. In addition, the rate of calcite crystal formation was also accelerated using recombinant NCA. Moreover, non-purified crude recombinant NCA also showed relatively significant ability. Therefore, recombinant CA could be an effective, economical biocatalyst in practical CO(2) conversion system.

Isolation of bacteria whose growth is dependent on high levels of CO2 and implications of their potential diversity

Although some bacteria require an atmosphere with high CO(2) levels for their growth, CO(2) is not generally supplied to conventional screening cultures. Here, we isolated 84 bacterial strains exhibiting high-CO(2) dependence. Their phylogenetic affiliations imply that high-CO(2) culture has potential as an effective method to isolate unknown microorganisms.

Brain abscess due to Actinobacillus actinomycetemcomitans. Case report

Actinobacillus actinomycetemcomitans, a constituent of the oral flora, is a rare cause of brain abscesses. We report the case of a 47-year-old male who presented with multiple brain abscesses due to this organism, presumably originating from his poor dentition. Problems met in isolating and identifying A. actinomycetemcomitans suggest that its true rate of isolation from non-oral samples may have been underestimated.

The biology of the gonococcus

Gonorrhea has been known since antiquity. Today, this disease is the most commonly reported infectious disease in the U.S. The natural environment of the etiological agent, Neisseria gonorrhoeae, is man. In this host, the organism usually parasitizes mucosal surfaces populated by columnar epithelial cells. Under certain conditions, the gonococcus may disseminate or spread to adjacent organs. The gonococcus is well adapted to its environment and is a successful parasite. Until recently, gonococci were uniformly sensitive to penicilin. However, a plasmid encoding beta-lactamase has been identified in some isolates. Most strains exhibit specific requirements for various amino acids, vitamins, purines, and pyrimidines. Only glucose, pyruvate, and lactate are utilized as sources of energy. Glucose is dissimilated by a combination of the Entner-Doudoroff and pentose phosphate pathways. A tricarboxylic acid cycle is also present and active under certain conditions. Structurally, the cell envelope of the gonococcus resembles that of a typical Gram-negative bacterium. Gonococci are highly autolytic, especially in older cultures or after depletion of the energy source. Autolysis is not due solely to peptidoglycan hydrolysis, but appears to involve a destabilization of the outer membrane as well. Cell surface components such as pili, lipopolysaccharide, outer membrane proteins, and a capsule are associated with the virulence and pathogenicity of this organism.