Pathogenic Bacterial Infections Research Articles

Treatment of Multi-Drug Resistant Gram-Negative Bacterial Pathogenic Infections

The multidrug-resistant Gram-negative bacteria (MDR-GNB) infections in severely infected patients present numerous difficulties in terms of treatment failure where antibiotics cannot arrest such drug resistant bacteria. Based on the patient’s medical history and updated microbiological epidemiology data, an effective empirical treatment remains critical for optimal results to safeguard human health. The aim of this manuscript is to review management of MDR-Gram negative pathogenic bacterial infections. Quick diagnosis and narrow antimicrobial spectrum require rapid and timely diagnosis and effective laboratories in accordance with antimicrobial stewardship (AS) principles. Worldwide, there is an increased emergence of Carbapenem-resistant Enterobacteriaceae (CRE), Pseudomonas aeruginosa, and Acinetobacter baumannii. Recently, novel therapeutic options, such as meropenem/vaborbactam, ceftazidime/avibactam, ceftolozane/tazobactam, eravacycline and plazomicin became accessible to effectively counteract severe infections. Optimally using these delays the emergence of resistance to novel therapeutic agents. Further study is required, however, due to uncertainties in pharmacokinetic/pharmacodynamics optimization of dosages and therapeutic duration in severely ill patients. The novel agents should be verified for (i) action on carbapenem resistant Acinetobacter baumannii; (ii) action on CRE of β-lactam/β-lactamase inhibitors dependence on type of carbapenemase; (iii) emergence of resistance to novel antibacterials and dismiss selective pressure promoting development of resistance. Alternative treatments should be approached alike phage therapy or antibacterial peptides. The choice of empirical therapy is complicated by antibiotic resistance and can be combated by accurate antibiotic and their combinations usage, which is critical to patient survival. Noteworthy are local epidemiology, effective teamwork and antibiotic stewardship to guarantee that medications are utilized properly to counter the resistance.

Salmonella Infection Among Food Handlers at Canteens in a Campus

Background: Salmonella is one of the pathogenic microorganisms that can contaminate food through cross-contamination (less hygiene of handlers and environment). In a campus, food management and food handlers have a very important role in the contamination of microorganisms, which can lead to the incidence of foodborne diseases. Objective: This study aimed to assess the incidence of salmonella infections among food handlers at a campus canteen in Depok City, Indonesia. Methods: The cross-sectional study was conducted in May-June 2017. The population of this study was all food handlers working in the canteen (N=260). The data were obtained through interviews and observation of the characteristics and behaviors of the food handlers. Blood samples were also collected from 49 food handlers (n=49). Results: This study revealed that 61.2% of food handlers included in the age group were not at risk, the proportion of female food-handlers was slightly more than men (51%), the majority of them were low educated (59.2%), and all respondents had never given typhoid immunization. The results of the fecal examination revealed that two food handlers had typhoid. In addition, the behavior and personal hygiene of most of the handlers are poor. Environmental factors such as canteen sanitation facilities are mostly qualified, and most of the food handlers have no history of contact with animals. Conclusion: There was no statistically significant relationship between characteristics, behavior, personal hygiene, sanitation facilities, and contact history with animals against pathogenic bacterial infections.

Innate Lymphoid Cells: Important Regulators of Host-Bacteria Interaction for Border Defense.

Innate lymphoid cells (ILCs) are a recently discovered type of innate immune lymphocyte. They include three different groups classified by the nature of the transcription factors required for their development and by the cytokines they produce. ILCs mainly reside in tissues close to the mucosal barrier such as the respiratory and gastrointestinal tracts. Due to their close proximity to the mucosal surface, ILCs are exposed to a variety of both commensal and pathogenic bacteria. Under non-pathological conditions, ILCs have been shown to be important regulators for the maintenance of tissue homeostasis by mutual interactions with the microbiome. Besides these important functions at homeostasis, several studies have also provided emerging evidence that ILCs contribute to defense against pathogenic bacterial infection by responding rapidly to the pathogens as well as orchestrating other immune cells. In this review, we summarize recent advances in our understanding of the interactions of ILCs and bacteria, with special focus on the function of the different ILC subsets in bacterial infections.

Isolation and Expression Analysis of a WRKY Transcription Factor in Sweet potato

A new WRKY transcription factor gene was isolated by ESTs screening from a cDNA library of suspension cultured cells of Sweet potato (Ipomoea batatas). The 2,285 bp cDNA fragment, IbWRKY, was sequenced, from which a 505 amino acid residue protein was deduced. A search of the protein BLAST database identified significant similarity to other plant WRKY31 protein sequences. RT-PCR analysis showed expression patterns of IbWRKY31 in various intact tissues and suspension cultured cells of Sweet potato, and in leaves exposed to different stresses. The IbWRKY31 gene was highly expressed in suspension cultured cells. In leaf tissues, IbWRKY31 showed strong expression during salicylic acid and methyl jasmonate treatments. Expression of IbWRKY31 was also induced under various abiotic stress and pathogen infection conditions, such as wounding, H2O2, MV, PEG, NaCl, and bacterial pathogen infection. These results suggest that IbWRKY31 is involved in plant responses to various stress conditions, such as abiotic stresses and pathogen infection through a defense signaling pathway.

The role of the microbiome and the NLRP3 inflammasome in the gut and lung.

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome, is one of the most well-characterized inflammasomes, activated by pathogen-associated molecular patterns and damage-associated molecular patterns, including from commensal or pathogenic bacterial and viral infections. The NLRP3 inflammasome promotes inflammatory cell recruitment and regulates immune responses in tissues such as the gastrointestinal tract and the lung, and is involved in many diseases that affect the gut and lung. Recently, the microbiome in the gut and the lung, and the crosstalk between these organs (gut-lung axis), has been identified as a potential mechanism that may influence disease in a bidirectional manner. In this review, we focus on themes presented in this area at the 2019 World Congress on Inflammation. We discuss recent evidence on how the microbiome can affect NLRP3 inflammasome responses in the gut and lung, the role of this inflammasome in regulating gut and lung inflammation in disease, and its potential role in the gut-lung axis. We highlight the exponential increase in our understanding of the NLRP3 inflammasome due to the synthesis of the NLRP3 inflammasome inhibitor, MCC950, and propose future studies that may further elucidate the roles of the NLRP3 inflammasome in gut and lung diseases.

Risk of bacterial foodborne pathogen infection among gastroenteritis cases in Qatar

Foodborne illness has been determined to be one of the major limitations to the advancement of world health. Bacterial pathogens among the leading causes of foodborne illness are Escherichia coli (E. coli), Campylobacter, Salmonella, and Listeria. The risk of these pathogens was investigated among gastroenteritis cases in the diverse population of the state of Qatar. Fecal samples from patients admitted to Hamad Medical Corporation (HMC) with complaints of gastroenteritis were screened for the targeted pathogens using a combination of bacterial enrichments and molecular detection. Salmonella was the most common pathogen (42.9%), followed by E. coli (35.3%), and Campylobacter (21.0%). C. jejuni was the most common species of Campylobacter (67.4%). The probability of detection of E. coli decreased with age. Meanwhile, both probabilities of detection of Campylobacter and Salmonella increased with age. Listeria monocytogenes was much less common among gastroenteritis cases compared to the other pathogens.

Deciphering the Novel Role of AtMIN7 in Cuticle Formation and Defense against the Bacterial Pathogen Infection.

The cuticle is the outermost layer of plant aerial tissue that interacts with the environment and protects plants against water loss and various biotic and abiotic stresses. ADP ribosylation factor guanine nucleotide exchange factor proteins (ARF-GEFs) are key components of the vesicle trafficking system. Our study discovers that AtMIN7, an Arabidopsis ARF-GEF, is critical for cuticle formation and related leaf surface defense against the bacterial pathogen Pseudomonas syringae pathovar tomato (Pto). Our transmission electron microscopy and scanning electron microscopy studies indicate that the atmin7 mutant leaves have a thinner cuticular layer, defective stomata structure, and impaired cuticle ledge of stomata compared to the leaves of wild type plants. GC–MS analysis further revealed that the amount of cutin monomers was significantly reduced in atmin7 mutant plants. Furthermore, the exogenous application of either of three plant hormones—salicylic acid, jasmonic acid, or abscisic acid—enhanced the cuticle formation in atmin7 mutant leaves and the related defense responses to the bacterial Pto infection. Thus, transport of cutin-related components by AtMIN7 may contribute to its impact on cuticle formation and related defense function.

Heme oxygenase 1 plays a crucial role in swamp eel response to oxidative stress induced by cadmium exposure or Aeromonas hydrophila infection.

Oxidative stress contributes a lot to initiation and progression of pathological conditions. Heme oxygenase 1 (HO1), a cytoprotective enzyme, is usually upregulated to alleviate oxidative stress in vivo. The function of teleost HO1 in the response to oxidative stress induced by heavy metal exposure and in pathogenic bacterial infection remains uncertain. In the present study, both complementary DNA and genomic sequence of a HO1-like gene cloned from the liver of swamp eel (Monopterus albus) are reported. Sequence analysis showed that the putative amino acid sequence contained a conserved heme oxygenase signature and displayed higher similarity to HO1 genes of other teleosts. Expression profile of swamp eel HO1 was investigated in healthy tissues and in tissues following stimulation with pathogenic bacteria (Aeromonas hydrophila) or cadmium chloride (CdCl2) exposure. Results demonstrated that HO1 messenger RNA (mRNA) was highly expressed in the liver and relatively less in other tissues. Bacterial infection with A. hydrophila significantly changed HO1 mRNA expression in the liver, spleen, and kidney, and the mRNA expression of HO1 and Nrf2 in the liver was elevated after the fish were exposed to CdCl2. Subsequently, the swamp eel HO1 was subcloned into a pET28a expression vector and transformed into Escherichia coli BL21 (DE3). Recombinant HO1 (rHO1) was successfully induced by 0.1mmol/l IPTG and purified by Ni-NTA His Bind Resin purification system. To determine whether the rHO1 could confer stress tolerance in vitro, the viability of control and HO1-expressing E. coli under CdCl2 stress was compared by spot assay. The rHO1 protein significantly increased survival rates of the bacterial hosts. To evaluate whether intraperitoneal injection with rHO1 protected the liver of swamp eel against A. hydrophila-induced oxidative stress, mRNA expression of HO1, Nrf2, hepcidin, and IL-1β as well as the oxidative stress-related parameters (ROS and total antioxidant capacity (T-AOC)) in the liver were examined. The results showed that exogenous rHO1 could significantly upgrade the mRNA expression of HO1 and hepcidin, coupled with increased ROS and T-AOC levels. However, Nrf2 and IL-1β expression levels were significantly downregulated and upregulated, respectively. These results suggested that HO1 should not only play a protective role in oxidative stress response and its adverse effects deserved further investigation.

Gram-Negative Bacterial Endotoxin LPS Induces NeuGc Loss through Ets1-Dependent Downregulation of Intestine-Specific pcmah Transcript in Porcine Intestinal Cells.

N-glycolylneuraminic acid (NeuGc), a non-human sialic acid derivative synthesized by cytidine-5′-monophospho-N-acetylneuraminic acid hydroxylase (CMAH), plays a crucial role in mediating infections by certain pathogens. Although it has been postulated that NeuGc biosynthesis and CMAH expression are downregulated during microbial infection, the underlying mechanisms remain unclear. The present study showed that exposure to lipopolysaccharide (LPS), a Gram-negative bacterial endotoxin, leads to loss of NeuGc biosynthesis in pig small intestinal I2I-2I cells. This LPS-induced NeuGc loss was accompanied by decreased CMAH transcript levels, especially intestine-specific 5′pcmah-1. Furthermore, LPS suppressed the activity of the Pi promoter responsible for 5′pcmah-1 by inhibiting DNA binding of Est1. These findings provide insight into the regulatory mechanisms of Neu5Gc biosynthesis during pathogenic infectious events, which may represent a host defense mechanism that protects the self against pathogenic bacterial infections even in non-sanitary environments.

Evaluation of Susceptibility Profiles of Some Bacteria to Flouroquinolones in Kano Metropolis, Nigeria

Resistance to broad spectrum antibiotics such as flouroquinolones by bacteria is becoming a major threats towards the chemotherapy of some common pathogenic bacterial infections in the world especially the developing nations. In view of that, susceptibility profiles of some pathogenic bacteria to some flouroquinolones were evaluated using modified Kirby-Bauer Disc Diffusion Technique. Four flouroquinolones antibiotics; ofloxacin and ciprofloxacin (second generation), levofloxacin (third generation), moxifloxacin (fourth generation) were tested on five bacterial species (Staphyllococcusaureus, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Klebsiella pneumoniae) sourced from Aminu Kano Teaching Hospital, Kano, Nigeria, and re-confirmed at Microbiology Laboratory in Bayero University, Kano. The results of the study revealed that 8(26.7%) of E. faecalis isolates were sensitive levofloxacin, 6(20.0%) were saensitive to ciprofloxacin and 1(3.33%) were sensitive to ofloxacin, while 0(0.00%) was sensitive to moxifloxacin. Seven isolates (23.3%) of S. aureus were sensitive to levofloxacin, 15(50.0%) were sensitive to ciprofloxacin and 4(13.3%) were sensitive to ofloxacin, while none (100%) were sensitive to moxifloxacin. E. coli isolates were 96.6% resistant to levofloxacin, Klebsiella pneumoniae and P. aeruginosa isolates exhibited 76.6 and 50.0% resistance to the antibiotic respectively. There was significant difference in the performance of the four antibiotics used, ciprofloxacin better than others (p-value 0.00604). There was no significant difference in the percentages of sensitive bacterial species to the antibiotics used in the research (p-value 0.614), however, P. aeruginosa showed relatively higher number of sensitive isolates 30(40%). It can be concluded that 58% of the isolates were moderately sensitive to all the antibiotics in this study.

Comparison of the Gut Microbiota Between Pulsatilla Decoction and Levofloxacin Hydrochloride Therapy on Escherichia coli Infection.

Gut microbiota serves as a critical indicator for gut health during treatment of pathogenic bacterial infection. Both Pulsatilla Decoction (abbreviated to PD, a traditional Chinese medicine compound) and Levofloxacin Hydrochloride (LVX) were known to have therapeutic effects to intestinal infectious disease. However, the changes of gut microbiota after PD or LVX treatment remain unclear. Herein, this work aimed to investigate the changes of intestinal flora after PD or LVX therapy of Escherichia coli infection in rats. Results revealed that PD exhibited a valid therapeutic approach for E. coli infection via the intestinal protection, as well as the inhibited release of IL-8 and ICAM-1. Besides, PD was beneficial to rebuild the gut microbiota via restoring Bacteroidetes spp in the composition of the gut microbiota. Comparatively, LVX treatment promoted the infection and ravaged gut microbiota by significantly decreasing Bacteroidetes and increasing Firmicutes. These findings not only highlight the mechanism of Chinese herbal formula, but extend the application of PD as veterinary medicine, feed additive and pre-mixing agent for improving the production of animal derived foods.

A bacterial infection-microenvironment activated nanoplatform based on spiropyran-conjugated glycoclusters for imaging and eliminating of the biofilm

A broad spectrum of microbial persistent infections is associated with bacterial biofilm which is difficult to be eliminated. In the clinic, diagnosis of biofilm-associated infections is heavily dependent on culturing methods which are difficult to identify pathogenic bacterial infection in vivo. Here, a facile bioreponsive nanoplatform consisting of spiropyran and galactose was developed for selectively imaging and eliminating the biofilm in situ. The nanoplatform could specially bind to bacteria through carbohydrate-protein interaction and rapidly respond to bacterial infection-microenvironment, finally imaging and eliminating biofilm. Importantly, the bioinspired nanoplatform is highly selective towards bacterial cells rather than mammalian cells with low toxicity against A549 cells. Collectively, this multifunctional nanoplatform as an imaging and dispersing biofilm agent provides promising insights for the development of the new treatment of biofilm-associated infections.

Lotus-leaf-inspired hierarchical structured surface with non-fouling and mechanical bactericidal performances

Antibiotics, a power tool to combat pathogenic bacterial infection, have experienced their inability to kill drug-resistant bacteria due to the development of antibiotic resistance. As an alternative, nanostructured, mechanical bactericidal surfaces may hold promise in killing bacteria without triggering antimicrobial resistance; however, accumulation of dead bacteria would greatly reduce their antimicrobial activity. In this study, for the first time we report a surprising discovery that the lotus leaf, well known for its superhydrophobicity, has demonstrated not only strong repelling effect against bacteria but also bactericidal activity via a cell-rupturing mechanism. Inspired by this unexpected finding, we subsequently designed and prepared a hierarchically structured surface, which was rendered superhydrophobic (water contact angle: 174°; roll-off angle: <1°) upon surface perfluorination. The hierarchically structured surface has displayed remarkable synergistic antimicrobial activity against Escherichia coli: while the majority of the bacteria (>99%) were repelled from the surface (non-fouling), those tenacious bacteria that managed to be in touch of the surface were physically killed completely. Compared to a conventional superhydrophobic surface (non-fouling to some extent, but no bacteria-killing) or a mechanical bactericidal surface (bacteria-killing but not bacteria-repelling), our new structured surface has the great advantage in maintaining long-term effectiveness in antimicrobial activity based entirely on physical mechanism.

In Situ Fabrication of Ultrasmall Gold Nanoparticles/2D MOFs Hybrid as Nanozyme for Antibacterial Therapy.

As one of the common reactive oxygen species, H2 O2 has been widely used for combating pathogenic bacterial infections. However, the high dosage of H2 O2 can induce undesired damages to normal tissues and delay wound healing. In this regard, peroxidase-like nanomaterials serve as promising nanozymes, thanks to their positive promotion toward the antibacterial performance of H2 O2 , while avoiding the toxicity caused by the high concentrations of H2 O2 . In this work, ultrasmall Au nanoparticles (UsAuNPs) are grown on ultrathin 2D metal-organic frameworks (MOFs) via in situ reduction. The formed UsAuNPs/MOFs hybrid features both the advantages of UsAuNPs and ultrathin 2D MOFs, displaying a remarkable peroxidase-like activity toward H2 O2 decomposition into toxic hydroxyl radicals (·OH). Results show that the as-prepared UsAuNPs/MOFs nanozyme exhibits excellent antibacterial properties against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria with the assistance of a low dosage of H2 O2 . Animal experiments indicate that this hybrid material can effectively facilitate wound healing with good biocompatibility. This study reveals the promising potential of a hybrid nanozyme for antibacterial therapy and holds great promise for future clinical applications.

Infection of Salmonella sp. in Gastrointestinal Tract of Magelang Duck Reared Intensively and Semi-intensively

The digestive tract is the main health center of an animal. When the balance of microflora in the digestive tract is disturbed, it becomes susceptible to be infected with pathogenic bacteria. This research was conducted to examine the effect of intensive and semi-intensive type of maintenance on the amount of Salmonella sp. on the profile of the Magelang duck digestive tract. Total contamination of Salmonella sp. and the total bacteria in the Magelang duck intestine were tested according to SNI 2897-2008. This research is a step that can be used to help farmer deal with the problem of pathogenic bacterial infections in a pattern of maintenance that is suspected to have high Salmonella contamination. Based on research that has been done, it can be concluded that neither the maintenance of intensive or semi-intensive ducks does not indicate the presence of Salmonella sp. From the two maintenance systems, it is obtained that the semi-intensive maintenance of Magelang ducks shows the number of digestive tract microflora which is higher than intensive maintenance. Keywords : Magelang duck, Salmonella sp.

Antibacterial Activity of Traditional Medicine &lt;i&gt;Scurrula atropurpurea&lt;/i&gt; (BL) DANS and their Endophytic Fungi

Scurrula atropurpurea known as benalu is a medicinal plant that has been used for the treatment of various diseases such as antibacterial. Plants with ethnomedicine history use to cure pathogenic bacterial infections and their endophytic fungi is a promising source of antibacterial compounds. This study aimed to compared the antibacterial activity of S. atropurpurea leaves and their endophytic fungi. The secondary metabolites were isolated from the leaves of S. atropurpurea and their endophytic fungi by the chromatography method. The antibacterial activity test was carried out by Kirby Bauer method against Salmonella typhi (IPCCCB.11.669) and Escherichia coli (ATCC 25922) as Gram (-) and Bacillus subtilis (ATCC 6633) and Staphylococcus aureus (ATCC 25923) as Gram (+). The antibacterial compound from S. atropurpurea was determined by spectroscopy analysis as Quercetin-3-O-α-L-Rhamnopyranoside, while the antibacterial compound from endophytic fungi (strain BB1) as a lactone. Phylogenetic tree of strain BB1 has the highest homology with Neopestalotiopsis surinamensis strain CBS 450.74.

Serratia marcescens: a key pathogen caused ginger rhizomes soft rot disease

Ginger is an important horticultural crop with high economic and nutritional value. However, it is prone to pathogenic bacterial infection that negatively affects growth, post-harvest quality, and reduced economic profits. The study of pathogenic bacteria associated with ginger disease through its productive life cycle is extremely valuable. In this study, we isolated a key pathogen Serratia marcescens from diseased ginger rhizomes. Koch’s postulates helped verify that S. marcescens provoked disease symptoms in ginger rhizomes and seedlings. Antioxidant enzyme activities of the host were markedly increased following S. marcescens infection rhizomes. Disease incidence of seedlings was 87.3% ± 3.05, and the disease severity index was 27.1 ± 1.2 after 15 days of root filling. Further, we verified that the isolated bacterium could infect rat peripheral nerve cells (RSC96), resulting cell lysis and death. All in all, we isolated a key pathogenic bacteria S. marcescens from rot rhizomes and analyzed its pathogenic features in ginger rhizomes and seedlings and its latent ability to infect mammalian cells. This study provides new information critical to managing ginger diseases caused by bacteria with a cross-kingdom infective cycle.

Poly(γ-glutamic acid)-based electrospun nanofibrous mats with photodynamic therapy for effectively combating wound infection.

Pathogenic bacterial infections associated with wound healing progress usually result in serious complications. Herein, biocompatible and antimicrobial electrospun nanofibrous mats with photodynamic therapy (PDT) effect were fabricated to accelerate the infected wound healing. The nanofibrous mats were fabricated by co-electrospining of polyanionic poly(γ-glutamic acid) (γ-PGA) and cationic photosensitizer 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra (p-toluenesulfonate) (TMPyP) in aqueous solution and stabilized by the chemical crosslinking. The as-prepared nanofibrous mats can not only confer the moist microenvironment to the wound bed, but also provide potent bactericidal activity upon visible light irradiation by releasing the cytotoxic reactive oxygen species (ROS). The antibacterial assay in vitro showed that they can effectively eradicate the board-spectrum bacteria at a relatively low loading dose of TMPyP (e.g., 0.1wt%). Meanwhile, those nanofibrous mats showed good biocompatibility with no obvious adverse effects on mammalian cells and red blood cells (RBCs). The animal test in vivo suggested that the restrained inflammatory reaction and better wound healing could be achieved upon timely and effective antibacterial treatment with negligible local toxicities. This biocompatible and antibacterial γ-PGA-TMPyP nanofibrous mat may show great potential in practical infection-resistant applications, particularly for wound dressing applications.

Effect of pathogenic bacteria on a novel C-type lectin, hemocyte and superoxide dismutase/ alkaline phosphatase activity in Onchidium reevesii

Bacterial infection in the marine environment is a serious problem to maintain the stability of marine ecosystems. Nevertheless, there is little report so far for the biological effects of pathogenic bacteria in coastal ecosystems. Hence, we investigated the responses of shell-less Onchidium reevesii to resist against pathogenic bacterial infection. Analysis of data here could be used as fundamental information for assessment of innate immune response of O. reevesii. The full-length OrCTL cDNA was cloned and consists of 1849 base pair (bp) encoding protein of 192 amino acids. Constructing multiple alignments suggested that OrCTL has conserved carbohydrate recognition domain (CRD) of CTLs, containing an EPS (Glu-Pro-Ser) motif that may imply the function of recognition of carbohydrates like others invertebrate. OrCTL mRNAs were mainly detected in ganglion and hepatopancreas, and expression was highly up-regulated from 2 h after Vibrio harveyi challenge, rapidly decreased at 4 h, and significantly increased at 12 h. In addition, after challenge with Vibrio parahaemolytics, OrCTL gene expression was slightly up-regulated from 2 h, peaked at 12 h. Enzyme activity (in the hepatopancreas) and cell immune (in the hemolymph) were investigated along with Superoxide dismutase (SOD) activity, alkaline phosphatase (ALP) activity and cell cycle. SOD activities were significantly higher after V. harveyi and V. parahaemolytics challenge than that in the control group, respectively. By contrast, ALP activities were significantly inhibited after challenged with bacteria than that in the control group, respectively. Enzyme activities in the hepatopancreas obviously fluctuated, and ALP activity was more sensitive to bacteria. Cell responses illustrated that there were a significant higher percentage of cells in the S and G2/M phase in hemolymph after challenged with bacteria. Our results suggested that the immune response of O. reevesii could be activated by pathogenic bacteria, and the data will provide referent for the disease prevention of systematic investigation in aquatic animal.

Introduction of the Menaquinone Biosynthetic Pathway into Rhodobacter sphaeroides and de Novo Synthesis of Menaquinone for Incorporation into Heterologously Expressed Integral Membrane Proteins.

Quinones are redox-active molecules that transport electrons and protons in organelles and cell membranes during respiration and photosynthesis. In addition to the fundamental importance of these processes in supporting life, there has been considerable interest in exploiting their mechanisms for diverse applications ranging from medical advances to innovative biotechnologies. Such applications include novel treatments to target pathogenic bacterial infections and fabricating biohybrid solar cells as an alternative renewable energy source. Ubiquinone (UQ) is the predominant charge-transfer mediator in both respiration and photosynthesis. Other quinones, such as menaquinone (MK), are additional or alternative redox mediators, for example in bacterial photosynthesis of species such as Thermochromatium tepidum and Chloroflexus aurantiacus. Rhodobacter sphaeroides has been used extensively to study electron transfer processes, and recently as a platform to produce integral membrane proteins from other species. To expand the diversity of redox mediators in R. sphaeroides, nine Escherichia coli genes encoding the synthesis of MK from chorismate and polyprenyl diphosphate were assembled into a synthetic operon in a newly designed expression plasmid. We show that the menFDHBCE, menI, menA, and ubiE genes are sufficient for MK synthesis when expressed in R. sphaeroides cells, on the basis of high performance liquid chromatography and mass spectrometry. The T. tepidum and C. aurantiacus photosynthetic reaction centers produced in R. sphaeroides were found to contain MK. We also measured in vitro charge recombination kinetics of the T. tepidum reaction center to demonstrate that the MK is redox-active and incorporated into the QA pocket of this heterologously expressed reaction center.