Ixotrophy is a process that enables certain microbes to prey on other cells. The ability of cells to aggregate or adhere is thought to be a significant initial step in ixotrophy. The gliding, multicellular filamentous bacterium Aureispira sp. CCB-QB1 belongs to the family Saprospiraceae and preys on bacteria such as Vibrio sp. in seawater. Adhesion and cell aggregation were coincident with preying and were hypothesized to play an important role in the ixotrophy in this bacterium. To test this hypothesis, experiments to elucidate the mechanisms of aggregation or adhesion in this bacterium were performed. The ability of Aureispira QB1 to adhere and aggregate to prey bacterium, Vibrio sp., required divalent cations, especially calcium ions. In the presence of calcium, Aureispira QB1 cells captured 99 % of Vibrio sp. cells after 60 min of incubation. Toluidine blue O, which binds acidic polysaccharides, bound to Aureispira QB1 and inhibited adhesion of Aureispira QB1. These results suggest that acidic polysaccharides are needed for aggregation or adhesion of Aureispira and that calcium ions play a significant role in these phenomena.
The gene coding for the oxygenase component, sadA, of 4-aminobenzenesulfonate (4-ABS) 3,4-dioxygenase in Hydrogenophaga sp. PBC was previously identified via transposon mutagenesis. Expression of wild-type sadA in trans restored the ability of the sadA mutant to grow on 4-ABS. The inclusion of sadB and sadD, coding for a putative glutamine-synthetase-like protein and a plant-type ferredoxin, respectively, further improved the efficiency of 4-ABS degradation. Transcription analysis using the gfp promoter probe plasmid showed that sadABD was expressed during growth on 4-ABS and 4-sulfocatechol. Heterologous expression of sadABD in Escherichia coli led to the biotransformation of 4-ABS to a metabolite which shared a similar retention time and UV/vis profile with 4-sulfocatechol. The putative reductase gene sadC was isolated via degenerate PCR and expression of sadC and sadABD in E. coli led to maximal 4-ABS biotransformation. In E. coli, the deletion of sadB completely eliminated dioxygenase activity while the deletion of sadC or sadD led to a decrease in dioxygenase activity. Phylogenetic analysis of SadB showed that it is closely related to the glutamine-synthetase-like proteins involved in the aniline degradation pathway. This is the first discovery, to our knowledge, of the functional genetic components for 4-ABS aromatic ring hydroxylation in the bacterial domain.
Isozymes of 23 cultures of the anaerobic rumen fungi and seven cultures of aerobic chytridiomycete fungi were analysed by PAGE. A total of 14 isozyme loci were successfully typed by PAGE. They were peptidase A & C-1, peptidase A & C-2, peptidase D-1, peptidase D-2, malate dehydrogenase-1, malate dehydrogenase-2, esterase-1, esterase-2, malic enzyme-1, malic enzyme-2, isocitrate dehydrogenase, shikimate dehydrogenase, phosphoglucomutase and 6-phosphogluconate dehydrogenase. Isozyme analysis can be used for studying the genetic relationships among the different anaerobic rumen fungi and the aerobic chytridiomycete fungi and the isozyme characteristics can serve as additional taxonomic criteria in the classification of the anaerobic rumen fungi. A dendrogram based on the isozyme data demonstrated that the anaerobic rumen fungi formed a cluster, indicating a monophyletic group, distinctly separated from the aerobic chytridiomycete fungi. Piromyces communis and P. minutus showed a close relationship but P. spiralis showed a more distant relationship to both P. communis and P. minutus. Piromyces as a whole was more related to Caecomyces than to Neocallimastix. Orpinomyces was also found to be more related to Piromyces and Caecomyces than to Neocallimastix. Orpinomyces intercalaris C 70 from cattle showed large genetic variation from O. joyonii, indicating that it is a different species.
Antibiotic resistance has become a major public health problem throughout the world. The presence of antibiotic-resistant bacteria such as Staphylococcus aureus and antibiotic resistance genes (ARGs) in hospital wastewater is a cause for great concern today. In this study, 276 Staph. aureus isolates were recovered from hospital wastewater samples in Malaysia. All of the isolates were screened for susceptibility to nine different classes of antibiotics: ampicillin, ciprofloxacin, gentamicin, kanamycin, erythromycin, vancomycin, trimethoprim and sulfamethoxazole, chloramphenicol, tetracycline and nalidixic acid. Screening tests showed that 100 % of Staph.aureus isolates exhibited resistance against kanamycin, vancomycin, trimethoprim and sulfamethoxazole and nalidixic acid. Additionally, 91, 87, 50, 43, 11 and 8.7 % of isolates showed resistance against erythromycin, gentamicin, ciprofloxacin, ampicillin, chloramphenicol and tetracycline, respectively. Based on these results, 100 % of isolates demonstrated multidrug-resistant (MDR) characteristics, displaying resistance against more than three classes of antibiotics. Of 276 isolates, nine exhibited resistance to more than nine classes of tested antibiotics; these were selected for antibiotic susceptibility testing and examined for the presence of conserved ARGs. Interestingly, a high percentage of the selected MDR Staph.aureus isolates did not contain conserved ARGs. These results indicate that non-conserved MDR gene elements may have already spread into the environment in the tropics of Southeast Asia, and unique resistance mechanisms against several antibiotics may have evolved due to stable, moderate temperatures that support growth of bacteria throughout the year.
Epidemiological studies, using the probe Ca3, have shown that in a given patient population a single cluster of genetically related Candida albicans isolates usually predominates. The authors have investigated whether these local clusters are part of a single group, geographically widespread and highly prevalent as an aetiological agent of various types of candidiasis. An unrooted neighbour-joining tree of 266 infection-causing C. albicans isolates (each from a different individual) from 12 geographical regions in 6 countries was created, based on genetic distances generated by Ca3 fingerprinting. Thirty-seven per cent of all isolates formed a single genetically homogeneous cluster (cluster A). The remainder of isolates were genetically diverse. Using the maximum branch length within cluster A as a cut-off, they could be divided into 37 groups, whose prevalence ranged between 0.3% and 9%. Strains from cluster A were highly prevalent in all but one geographical region, with a mean prevalence across all regions of 41%. When isolates were separated into groups based on patient characteristics or type of infection, strains from cluster A had a prevalence exceeding 27% in each group, and their mean prevalence was 43% across all patient characteristics. These data provide evidence that cluster A constitutes a general-purpose genotype, which is geographically widespread and acts as a predominant aetiological agent of all forms of candidiasis in all categories of patients surveyed.
The biochemical events associated with the onset of lipid accumulation in Mucor circinelloides and Mortierella alpina, under conditions of nitrogen-limited growth, have been elucidated; they differ in key aspects from those described in oleaginous yeasts. The NAD+:isocitrate dehydrogenases of Mc. circinelloides and Mort. alpina were not absolutely dependent on AMP for activity. Furthermore, changes in the cellular adenine nucleotide pools and energy charge were different from those reported for oleaginous yeasts. In Mc. circinelloides ATP, ADP and AMP concentrations all decreased by 50% after nitrogen limitation, leading to a constant energy charge at the expense of the size of the total adenylate pool. Pyruvate carboxylase in Mc. circinelloides was cytosolic, having implications for the organization of lipid synthesis in filamentous fungi. As a result of the data obtained, a revised and more concerted mechanism for the initiation of storage lipid accumulation is put forward for filamentous fungi.
In recent years, oral probiotics have been researched on their effectiveness in reducing and preventing oral diseases. Oral probiotics could be introduced into the oral cavity to keep the equilibrium of the microbiome. Hence, the delivery carrier for oral probiotics plays an important factor to ensure a high number of oral probiotics were delivered and released into the oral cavity. This review presents a brief overview of oral microbiota and the role of oral probiotics in reducing oral diseases. Moreover, important aspects of the oral probiotic product such as viability, adherence ability, health effects, safety, and delivery site were discussed. Besides that, the importance of utilizing indigenous oral probiotics was also emphasized. Oral probiotics are commonly found in the market in the form of chewing tablets, lozenges, and capsules. Hence, the oral probiotic carriers currently used in the market and research were reviewed. Furthermore, this review introduces new potential oral probiotic delivery carriers such as oral strip, bucco-adhesive gel, and mouthwash. Their effectiveness in delivering oral probiotics for oral health was also explored.