Michael Apicella

University of Iowa | UI · Department of Microbiology

Several bacterial pathogens contain membrane ligands that facilitate their binding and internalization into human tissues. In this study, lipooligosaccharides (LOS) from the respiratory pathogen non-typeable Haemophilus influenzae (NTHi) were isolated from the bacterial surface and evaluated as a nanoparticle coating material to facilitate uptake i...

The lipooligosaccharide (LOS) of Neisseria gonorrhoeae plays key roles in pathogenesis and is composed of multiple possible glycoforms. These glycoforms are generated by the process of phase variation and by differences in the glycosyltransferase gene content of particular strains. LOS glycoforms of N. gonorrhoeae can be terminated with an N-acetyl...

Optimal innate immune response to infection includes eradication of potential pathogens, resolution of associated inflammation, and restitution of homeostasis. Phagocytosing human polymorphonuclear leukocytes (hPMN) undergo accelerated apoptosis, a process referred to as phagocytosis-induced cell death (PICD) and an early step in their clearance fr...

Neisseria gonorrhoeae is the causative agent of the sexually transmitted infection (STI) gonorrhea, a disease with high morbidity worldwide with an estimated 87 million cases annually. Current therapeutic and pharmacologic approaches to treat gonorrhea have been compromised by increased antibiotic resistance worldwide, including to the most recent...

Environmental pH can be an important cue for symbiotic bacteria as they colonize their eukaryotic hosts. Using the model mutualism between the marine bacterium Vibrio fischeri and the Hawaiian bobtail squid, we characterized the bacterial transcriptional response to acidic pH experienced during the shift from planktonic to host‐associated lifestyle...

Host-adapted bacterial pathogens such as NTHi cannot survive out of their host environment and have evolved host-specific mechanisms to obtain nutrients and evade the immune response. Relatively few of these host adaptations have been characterized at the molecular level. NTHi utilizes sialic acid as a nutrient and also incorporates this sugar into...

Neisseria gonorrhoeae is quickly becoming untreatable due to its acquisition of resistance to multiple antimicrobials. It is vital that we begin to understand the mechanisms by which this is occurring. The paper by C. E. Rouquette-Loughlin, J. L. Reimche, J. T. Balthazar, V. Dhulipala, et al. (mBio 9:e02281-18, https://doi.org/10.1128/mBio.02281-18...

The primary role of bacterial periplasmic binding proteins is sequestration of essential metabolites present at a low concentration in the periplasm and making them available for active transporters that transfer these ligands into the bacterial cell. The periplasmic binding proteins(SiaP) from the tripartite ATP-independent periplasmic (TRAP) tran...

Nontypeable Haemophilus influenzae (NTHi) is an important pathogen in individuals of all ages. The lipooligosaccharide (LOS) of NTHi has evolved a complex structure that can be attributed to a multiplicity of glycosyltransferases, the random switching of glycosyltransferase gene expression via phase variation, and the complex structure of its core...

Nontypeable Haemophilus influenzae (NTHi) has been shown to form biofilms, comprised of extracellular DNA (eDNA), in the middle ear and bronchus during clinical infections. Studies in our laboratory have shown that NTHi possesses a homolog of Staphylococcus aureus thermonuclease (staphylococcal thermonuclease), NTHi nuclease (NTHi Nuc, HI_1296). Th...

Post‐translational acetylation is a common protein modification in bacteria. It was recently reported that Neisseria gonorrhoeae acetylates the Type IV pilus retraction motor, PilT. Here, we show recombinant PilT can be acetylated in vitro and acetylation does not affect PilT ultrastructure. To investigate the function of PilT acetylation, we mutat...

Francisella tularensis is the causative agent of tularemia and a potential bioterrorism agent. In the present study, we isolated, identified, and quantified the proteins present in the membranes of the virulent type A strain, Schu S4, and the attenuated type B strain, LVS (live vaccine strain). Spectral counting of mass spectrometric data showed en...

Neisseria gonorrhoeae, the causative agent of gonorrhea, has a number of factors known to contribute to pathogenesis; however, a full understanding of these processes and their regulation has proven to be elusive. Post-translational modifications (PTMs) of bacterial proteins are now recognized as one mechanism of protein regulation. In the present...

All lysine acetylation sites and their corresponding motifs for all unique sites detected in all replicates. (XLSX)

Keyword enrichment for acetylated proteins with regulated acetylation sites. (XLSX)

Primers used in this study. (DOCX)

Mass spectrometric details for all identified acetyllysine-containing peptides identified with at least a confidence score of 99. (XLSX)

(Sheet A) List of proteins found in common between the AckA-dependent K-ac sites found in the current study with a previous study examining protein level changes between anaerobic/aerobic growth. A number of proteins were found in common between these studies. These proteins may represent proteins that are very responsive to changes in metabolism a...

Acetylated proteins and number of acetylated sites detected in each protein overall. (XLSX)

Comparisons of protein annotations from strains FA 1090 and 1291 of hypothetical proteins identified in FA 1090. (XLSX)

Average ratios of regulated acetylation sites. Regulated sites were defined as ones seen in at least two biological replicates, with at least a 2-fold increase in the acetylation level and a p-value< 0.05. (XLSX)

GO term enrichment for acetylated proteins with regulated acetylation sites. (XLSX)

Kegg pathway enrichment for acetylated proteins with regulated acetylation sites. (XLSX)

Regulated lysine acetylated sites that are conserved in N. gonorrhoeae and E. coli. (XLSX)

Respiratory syncytial virus (RSV) and the common commensal and opportunistic pathogen, non-typeable Haemophilus influenzae (NTHi) both serve as a frequent cause of respiratory infection in children. Although it is well established that some respiratory viruses can increase host susceptibility to secondary bacterial infections, few studies have exam...

Importance: N. gonorrhoeae is the causative agent of the globally-prevalent sexually transmitted infection gonorrhea. An understudied aspect of this human-adapted pathogen is the changes in bacterial physiology that occur during sexual transmission. N. gonorrhoeae encounters semen when transmitted from host-to-host and it is known that when N. gon...

Previous studies have demonstrated that Neisseria gonorrhoeae sialylates the terminal N-acetyllactosamine present on its lipooligosaccharide (LOS) by acquiring CMP-N-acetyl-5-neuraminic acid upon entering human cells during infection. This renders the organism resistant to killing by complement in normal human serum. N-acetyllactosamine residues on...

Francisella tularensis, the Gram-negative bacterium that causes tularemia, produces a high molecular weight capsule that is immunologically distinct from Francisella lipopolysaccharide but contains the same O-antigen tetrasaccharide. To pursue the possibility that the capsule of Francisella live vaccine strain (LVS) has a structurally unique lipid...

Schema of methods used. A) Schematic representation of the method to isolate O-Ag capsule as described by Apicella et al. [4] B) Schematic of the method used herein to isolate EtOHp. (TIFF)

Recent research has shown that the microbiota affects the biology of associated host epithelial tissues, including their circadian rhythms, although few data are available on how such influences shape the microarchitecture of the brush border. The squid-vibrio system exhibits two modifications of the brush border that supports the symbionts: efface...

Haemophilus haemolyticus and nontypeable Haemophilus influenzae (NTHi) are closely related upper airway commensal bacteria that are difficult to distinguish phenotypically. NTHi causes upper and lower airway tract infections in individuals with compromised airways, while H. haemolyticus rarely causes such infections. The lipooligosaccharide (LOS) i...

Gonorrhea is a major, global public health problem for which there is no vaccine. The continuing emergence of antibiotic-resistant strains raises concerns that untreatable Neisseria gonorrhoeae may become widespread in the near future. Consequently, there is an urgent need for increased efforts towards the development of new anti-gonococcal therape...

Significance Pathogens use cell surface carbohydrates as a means of attachment to host tissues. In several pathogenic bacteria, truncation of surface carbohydrates, lipooligosaccharide, or lipopolysaccharide have been reported to significantly reduce bacterial adherence to host cells. Here, we show that the lipooligosaccharide/lipopolysaccharide of...

Unlabelled: Mammalian lipopolysaccharide (LPS) binding proteins (LBPs) occur mainly in extracellular fluids and promote LPS delivery to specific host cell receptors. The function of LBPs has been studied principally in the context of host defense; the possible role of LBPs in nonpathogenic host-microbe interactions has not been well characterized....

Introduction Gonorrhoea, one of the most common sexually transmitted infections worldwide, can lead to serious sequelae, including infertility and increased HIV transmission. Recently, untreatable, multidrug-resistant Neisseria gonorrhoeae strains have been reported. In the absence of new antibiotics, and given the speed with which resistance has e...

Gonorrhea, one of the most common sexually transmitted infections worldwide, can lead to serious sequelae, including infertility and increased HIV transmission. Recently, untreatable, multidrug-resistant Neisseria gonorrhoeae strains have been reported. In the absence of new antibiotics, and given the speed with which resistance has emerged to all...

Francisella tularensis is classified as a Tier 1 select agent by the CDC due to its low infectious dose and the possibility that the organism can be used as a bioweapon. The low dose of infection suggests that Francisella is unusually efficient at evading host defenses. Although ~50 cfu are necessary to cause human respiratory infection, the early...

Nontypeable Haemophilus influenzae (NTHi) forms biofilms in the middle ear during human infection. The biofilm matrix of NTHi contains extracellular DNA. In this paper, we show that NTHi possesses a potent nuclease, which is a homolog of the thermonuclease of Staphylococcus aureus. Using a biofilm dispersal assay, studies showed a biofilm dispersal...

Acute gonorrhea is characterized by neutrophilic inflammation that is insufficient to clear Neisseria gonorrhoeae (Gc). Activated neutrophils release extracellular traps (NETs), which are comprised of chromatin and decorated with antimicrobial proteins. The Gc NG0969 open reading frame encodes a putatively secreted thermonuclease (nuc) that contrib...

Background Non-typeable H. influenzae (NTHi) is a nasopharyngeal commensal that can become an opportunistic pathogen causing infections such as otitis media, pneumonia, and bronchitis. NTHi is known to form biofilms. Resistance of bacterial biofilms to clearance by host defense mechanisms and antibiotic treatments is well-established. In the curren...

Neisseria gonorrhoeae causes gonorrhea, a sexually transmitted infection characterized by inflammation of the cervix or urethra. However, a significant subset of patients with N. gonorrhoeae remain asymptomatic, without evidence of localized inflammation. Inflammatory responses to N. gonorrhoeae are generated by host innate immune recognition of N....

Well-differentiated human airway epithelia present formidable barriers to efficient siRNA delivery. We previously reported that treatment of airway epithelia with specific small molecules improves oligonucleotide uptake and facilitates RNAi responses. Here, we exploited the platelet activating factor receptor (PAFR) pathway, utilized by specific ba...

Sialic acids are a family of related nine-carbon sugar acids that play important roles in both eukaryotes and prokaryotes. These sialic acids are incorporated/decorated onto lipooligosaccharides as terminal sugars in multiple bacteria to evade the host immune system. Many pathogenic bacteria scavenge sialic acids from their host and use them for mo...

The acyl chain length, number and distribution have been considered the major factors contributing to this biological activity of Lipid A. The charged head groups on the dihexosamine backbone have also been implicated in contributing to this biology. In Neisseria, it has now been shown that loss of the 4' phosphoethanolamine impacts on virulence in...

Bacterial biofilms grow on many types of surfaces, including flat surfaces such as glass and metal and irregular surfaces such as rocks, biological tissues and polymers. While laser scanning confocal microscopy can provide high-resolution images of biofilms grown on any surface, quantification of biofilm-associated bacteria is currently limited to...

LPS is a major component of the outer membrane of Gram-negative bacteria. The lipid A region of LPS mediates stimulation of the immune system. In E. coli, the gene (formerly htrB) codes for a late lauroyltransferase (LpxL) in lipid A biosynthesis. E. coli lpxL mutants have been described previously with impaired growth above 33 in rich media. Howev...

The virulence factors mediating Francisella pathogenesis are being investigated, with an emphasis on understanding how the organism evades innate immunity mechanisms. Francisella tularensis produces a lipopolysaccharide (LPS) that is essentially inert and a polysaccharide capsule that helps the organism to evade detection by components of innate im...

Background: Studies of nontypeable Haemophilus influenzae (NTHi) have demonstrated that a number of genes associated with infectivity have long repeat regions associated with phase variation in expression of the respective gene. The purpose of this study was to determine the genes that underwent phase variation during a 6-day period of experimenta...

Background: Nontypeable Haemophilus influenzae (NTHi) exclusively infects humans, causing significant numbers of upper respiratory tract infections. The goal of this study was to develop a safe experimental human model of NTHi nasopharyngeal colonization. Methods: A novel streptomycin-resistant strain of NTHi was developed, and 15 subjects were...

Pili of pathogenic Neisseria are major virulence factors associated with adhesion, twitching motility, auto-aggregation, and DNA transformation. Pili of N. meningitidis are subject to several different post-translational modifications. Among these pilin modifications, the presence of phosphorylcholine (ChoP) and a glycan on the pilin protein are ph...

PilE gene sequence alignment of high TEPC-15 reactive colonies. The amino acid sequence, and sequence conservation surrounding the post-translational modifications of pilin, in Neisseria are shown. Superscript numbers represent the amino acid number in the mature pilin. The arrow indicates the site of trisaccharide addition. The variable structures...

The relative positions of phosphorylcholine and glycosylation post-translational modifications modelled on pilin subunit in Neisseria meningitidis . (MOV)

The relative positions of phosphorylcholine and glycosylation post-translational modifications of adjacent pilin subunits on pilus fibre in Neisseria meningitidis . (MOV)

PptA polymeric G screening of Neisseria MLST typed and clinical isolate strains. (DOCX)

Analysis of FLAG-tagged purified pilin. To undertake structural studies on ChoP modification of pilin, it is necessary to express and purify large quantities of pure, soluble pilin from N. meningitidis. In this study, pilin of N. meningitidis was purified using a Flag-tag-based system. Western Blot analysis of purified pilin was performed to confir...

Immunoprecipitation of PAFr and pili from various C311#3 mutants and variants. Immunoprecipitation followed by Western Blot analysis demonstrates that meningococci bind to the PAFr via an interaction involving both the pili-linked ChoP and glycan modifications. Following a 15 minute challenge of 16HBE14 human bronchial epithelial cells, captured an...

List of primers. (DOCX)

Bacteria strains used. (DOCX)

NtrYX is a sensor-histidine kinase/response regulator two-component system that has had limited characterization in a small number of Alphaproteobacteria. Phylogenetic analysis of the response regulator NtrX showed that this two-component system is extensively distributed across the bacterial domain, and it is present in a variety of Betaproteobact...

Author Summary Neisseria meningitidis is an important human pathogen that can cause rapidly progressing, life threatening meningitis and sepsis in humans. There is no fully protective vaccine against this pathogen in current use and the key processes that dictate the transition from harmless carriage of the bacterium in the airway (the case for the...

NtrYX is a sensor-histidine kinase/response regulator two-component system that has had limited characterization in a small number of Alphaproteobacteria. Phylogenetic analysis of the response regulator NtrX showed that this two-component system is extensively distributed across the bacterial domain, and it is present in a variety of Betaproteobact...

The symbiosis between the squid Euprymna scolopes and its luminous symbiont, Vibrio fischeri, is characterized by daily transcriptional rhythms in both partners and daily fluctuations in symbiont luminescence. In this study, we sought to determine whether symbionts affect host transcriptional rhythms. We identified two transcripts in host tissues (...

Alignment of the EsCry1 and other Cry1 proteins. Species names are shown to the left of the alignment, and the consensus sequence is shown at the bottom of each line. Dashes (-) indicate gaps in the alignment, and dots (.) indicate identity to the above residue. Boxes around particular residues indicate conservation of amino acids shown to be impor...

Primers used in this study.

Alignment of the EsCry2 and other Cry2 proteins. Species names are shown to the left of the alignment, and the consensus sequence is shown at the bottom of each line, above a bar graph showing the degree of conservation at each amino acid residue. Dashes (-) indicate gaps in the alignment, and dots (.) indicate identity to the above residue. Boxes...

The effect of lipid A or peptidoglycan monomer addition on light-organ escry1 expression. (a) Expression of escry1 in the light organs of uncolonized animals treated with 10 ng/ml V. fischeri lipid A in seawater exposed to exogenous blue light at two time points over the day/night cycle. (b) escry1 light-organ expression in animals exposed to exoge...

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##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

##Assembly-Data-START## Assembly Method :: SeqMan Pro v. 8.1.2 Sequencing Technology :: 454 ##Assembly-Data-END##

AniA of the pathogenic Neisseria is glycosylated in its C-terminal repeat region by the pilin glycosylation (pgl) pathway. AniA appears to be unique among bacterial nitrite reductases as it contains an N-terminal extension that includes a lipid modification site as well as a C-terminal extension that is glycosylated. Immunising with various glycofo...

Aim: The glutathione-dependent AdhC-EstD formaldehyde detoxification system is found in eukaryotes and prokaryotes. It is established that it confers protection against formaldehyde that is produced from environmental sources or methanol metabolism. Thus, its presence in the human host-adapted bacterial pathogen Neisseria meningitidis is intriguin...

Neisseria gonorrhoeae, the causative agent of gonorrhea, can form biofilms in vitro and in vivo. In biofilms, the organism is more resistant to antibiotic treatment and can serve as a reservoir for chronic infection. We have used stable isotope labeling by amino acids in cell culture (SILAC) to compare protein expression in biofilm and planktonic o...

KEGG pathway for pyruvate metabolism. Differentially expressed N. gonorrhoeae proteins from the present study and genes from the published transcriptional profiling study [30] that mapped to this KEGG pathway are color-coded on the pathway and listed in the Key. (PDF)

KEGG pathway for the citrate cycle (TCA cycle). Differentially expressed N. gonorrhoeae proteins from the present study and genes from the published transcriptional profiling study [30] that mapped to this KEGG pathway are color-coded on the pathway and listed in the Key. (PDF)

KEGG pathway glycolysis/gluconeogenesis. Differentially expressed N. gonorrhoeae proteins from the present study and genes from the published transcriptional profiling study [30] that mapped to this KEGG pathway are color-coded on the pathway and listed in the Key. (PDF)