Ultrastructure and SSU rDNA Phylogeny of Paraphysomonas vestita (Stokes) De Saedeleer Isolated from Laguna de Bay, Philippines

Paraphysomonas vestita is a unicellular, colorless, silica-scaled chrysophyte that plays an important ecological role in freshwater microbial communities as a consumer of prokaryotic and eukaryotic prey. There is little biogeographical information for this minute protist despite its significant role in aquatic food webs. In addition, the phylogenetic relationship of P. vestita to other taxa is unclear as P. vestita may be polyphyletic or a cryptic species complex. In this study, a clonal isolate from a freshwater sample of Laguna de Bay, Philippines was subjected to morphological study by electron microscopy and its small subunit ribosomal RNA (SSU rRNA) gene was sequenced. Morphological studies showed that the isolate possesses two unequal flagella emerging from the anterior part of the cell. Negative staining revealed the structure of the scales which consist of a baseplate with slightly thickened rim. The narrowing spine arises from the center of the baseplate. These results agree with previously studied isolates of P. vestita. The 18S rRNA gene sequence of the isolate had a very high similarity (99%) to P. vestita strain PV10. Phylogenetic analysis also showed that the isolate clustered with other Paraphysomonas sequences with high bootstrap support. Phylogenetic studies confirmed that P. vestita may be polyphyletic. No studies on the ultrastructure and phylogeny of a silica-scaled chrysophyte isolated in the Philippines have been reported so far. Results from this study may contribute to further ultrastructural and phylogenetic studies on aquatic flagellates and specifically to a revision of this potentially polyphyletic species

Genomic analysis of Salmonella enterica from Metropolitan Manila abattoirs and markets reveals insights into circulating virulence and antimicrobial resistance genotypes

The integration of next-generation sequencing into the identification and characterization of resistant and virulent strains as well as the routine surveillance of foodborne pathogens such as Salmonella enterica have not yet been accomplished in the Philippines. This study investigated the antimicrobial profiles, virulence, and susceptibility of the 105 S. enterica isolates from swine and chicken samples obtained from slaughterhouses and public wet markets in Metropolitan Manila using whole-genome sequence analysis. Four predominant serovars were identified in genotypic serotyping, namely, Infantis (26.7%), Anatum (19.1%), Rissen (18.1%), and London (13.3%). Phenotypic antimicrobial resistance (AMR) profiling revealed that 65% of the isolates were resistant to at least one antibiotic, 37% were multidrug resistant (MDR), and 57% were extended-spectrum β-lactamase producers. Bioinformatic analysis revealed that isolates had resistance genes and plasmids belonging to the Col and Inc plasmid families that confer resistance against tetracycline (64%), sulfonamide (56%), and streptomycin (56%). Further analyses revealed the presence of 155 virulence genes, 42 of which were serovar-specific. The virulence genes primarily code for host immune system modulators, iron acquisition enzyme complexes, host cell invasion proteins, as well as proteins that allow intracellular and intramacrophage survival. This study showed that virulent MDR S. enterica and several phenotypic and genotypic AMR patterns were present in the food chain. It serves as a foundation to understand the current AMR status in the Philippines food chain and to prompt the creation of preventative measures and efficient treatments against foodborne pathogens

Data on preparation of psychrotolerant bacterium Shewanella olleyana sp. nov. cells for transmission electron microscopy

This data article contains transmission electron microscopy (TEM) images of psychrotolerant bacterium Shewanella olleyana sp. nov. Cells of S. olleyana were grown following an optimized culture conditions in liquid medium. Procedure for the preparation of cells suitable for TEM is described in detail

Epigallocatechin gallate from Camellia sinensis L. (Kuntze) is a potential quorum sensing inhibitor in Chromobacterium violaceum

The problem on the widespread occurrence of antibiotic resistant strains of bacteria calls for novel methods of control of bacterial activity. One of the new viable alternatives to antibiotics is the use of substances that inhibit quorum sensing (QS) – a bacterial communication system that has been known to regulate the expression of virulence genes during infection. In this study, epigallocatechin gallate (EGCG) from green tea, Camellia sinensis L. (Kuntze) was tested for its ability to inhibit QS in a test organism, Chromobacterium violaceum. This microorganism produces a violet-colored substance, violacein, through QS. This study aimed to detect inhibition of QS-regulated violacein production in C. violaceum by EGCG and to determine the dynamics of QS inhibition relative to the concentration of EGCG. The effect of increasing concentration of EGCG on both violacein production and cell density of treated and untreated C. violaceum was determined in a 96-well-microplate format and read at 570nm and 620nm for violacein production and growth, respectively. The results show that addition of EGCG increased the growth of the organism while there is concentration-dependent decrease in the QS-controlled production of violacein. This study thus establishes that EGCG is a potential QS inhibitor and can be further studied and developed for its use as an anti-pathogenic but non-toxic drug

Field study on the distribution of Entamoeba histolytica and Entamoeba dispar in the northern Philippines as detected by the polymerase chain reaction

We used the polymerase chain reaction (PCR) to study the distribution of Entamoeba histolytica and E. dispar in 1,872 individuals in 14 communities in the northern Philippines. Here we report a field study using a DNA extraction protocol from formalin-fixed stool specimens as previously reported. This assay detected 137 stools (7.318%) containing E. dispar and 18 stools (0.961%) containing E. histolytica. The most affected age group for E. histolytica/E. dispar infections were those 5-14 years of age. There was no significant difference in the sex distribution of E. histolytica, while in the case of E. dispar, a higher prevalence was observed in females (9.186%) than in males (5.731%) (P < 0.01). An apparent clustering of stool-positive cases of E. histolytica and E. dispar was also observed in the northern part of the study area. The results of this survey demonstrate that E. dispar is highly prevalent in the communities studied. Moreover, it offers promise for the PCR using DNA extracted from formalin-fixed stools as a sensitive epidemiologic tool for detecting E. histolytica and E. dispar infections

Ultrastructure and SSU rDNA Phylogeny of Paraphysomonas vestita (Stokes) De Saedeleer Isolated from Laguna de Bay, Philippines

Paraphysomonas vestita is a unicellular, colorless, silica-scaled chrysophyte that plays an important ecological role in freshwater microbial communities as a consumer of prokaryotic and eukaryotic prey. There is little biogeographical information for this minute protist despite its significant role in aquatic food webs. In addition, the phylogenetic relationship of P. vestita to other taxa is unclear as P. vestita may be polyphyletic or a cryptic species complex. In this study, a clonal isolate from a freshwater sample of Laguna de Bay, Philippines was subjected to morphological study by electron microscopy and its small subunit ribosomal RNA (SSU rRNA) gene was sequenced. Morphological studies showed that the isolate possesses two unequal flagella emerging from the anterior part of the cell. Negative staining revealed the structure of the scales which consist of a baseplate with slightly thickened rim. The narrowing spine arises from the center of the baseplate. These results agree with previously studied isolates of P. vestita. The 18S rRNA gene sequence of the isolate had a very high similarity (99%) to P. vestita strain PV10. Phylogenetic analysis also showed that the isolate clustered with other Paraphysomonas sequences with high bootstrap support. Phylogenetic studies confirmed that P. vestita may be polyphyletic. No studies on the ultrastructure and phylogeny of a silica-scaled chrysophyte isolated in the Philippines have been reported so far. Results from this study may contribute to further ultrastructural and phylogenetic studies on aquatic flagellates and specifically to a revision of this potentially polyphyletic species

Activity of the ethanolic extract of propolis (EEP) as a potential inhibitor of quorum sensing-mediated pigment production in chromobacterium violaceum and virulence factor production in pseudomonas aeruginosa

Bacteria are capable of the organized expression of specific sets of genes through a recently discovered phenomenon termed quorum sensing (QS). Researchers are beginning to focus their efforts into the discovery of potential QS inhibitors for the development of novel antipathogenic drugs. This study investigated the QS inhibitory potential of the ethanolic extract of propolis (EEP) in the test organism Chromobacterium violaceum ATCC 12472 and the opportunistic organism Pseudomonas aeruginosa PAO1. Results of this study showed EEP as a potential inhibitor of QSmediated violacein production in C. violaceum. EEP was thereby subjected to further testing on its ability to interfere with virulence factor production and biofilm formation in P. aeruginosa. It was found that EEP was able to significantly affect the LasA and LasB protease activities. In addition, changes in the protease activity were observed with no significant effects on the growth of the organism. This implies that changes in the enzyme activities are unrelated to bactericidal consequences. However, it was also found that EEP inhibited the biofilm formation of P. aeruginosa PAO1 at lower concentrations but not at higher concentrations. This suggests the need for further investigations to be made on the effect of EEP on the maturation and differentiation of biofilms

In Silico Approaches for the Identification of Aptamer Binding Interactions to <i>Leptospira</i> spp. Cell Surface Proteins

Aptamers are nucleic acids that can bind with high affinity and specificity to a range of target molecules. However, their functionality relies on their secondary and tertiary structures such that the combination of nucleotides determines their three-dimensional conformation. In this study, the binding mechanisms of candidate aptamers and their interactions with selected target proteins found in the cell surface of Leptospira were predicted to select high-affinity aptamers. Four aptamers were evaluated through molecular modeling and docking using available software and web-based tools, following the workflow previously designed for in silico evaluation of DNA aptamers. The most predominant and highly conserved surface-exposed proteins among pathogenic Leptospira species were used as aptamer targets. The highest number of interactions was seen in aptamers AP5 and AP1. Hydrogen bonds, along with a few hydrophobic interactions, occur in most aptamer–protein complexes. Further analysis revealed serine, threonine, glutamine, and lysine as main protein residues. H-bond interactions occur mostly with polar amino acids, as reflected in the predicted interaction profiles of aptamer–protein complexes. In silico strategies allowed the identification of key residues crucial in aptamer–target interaction during aptamer screening. Such information can be used in aptamer modification for improved binding affinity and accuracy for diagnostics application