Utilization of -xylose as carbon source for production of bacterial cellulose

Utilization of -xylose as carbon source for production of bacterial cellulose was studied. Seventeen strains of acetic acid bacteria were screened for their cellulose productivity in -glucose, -xylose, and -xylose/ -xylulose mixed media, respectively. -Xylose was not well metabolized by any bacterial strains that exhibited high cellulose production in -glucose medium. Consequently, bacterial cellulose production in -xylose medium was unsuccessful. -Xylose, however, became utilizable substrate for bacterial strains if xylose-isomerase was added to the medium. Acetobacter xylinus IFO 15606 was the best cellulose producer in -xylose/ -xylulose mixed medium, so cultural conditions were studied for enhanced cellulose production. With pH controlled, the strain could produce cellulose at a yield exceeding 0.3 g per 100 ml of -xylose/ -xylulose mixed medium, which was comparable to the yields in -glucose medium by excellent producers in the literature.     

Bacterial bioluminescence as an early indication of marine fish spoilage

Summary The relationships between different microbiological and biochemical parameters and the development of bacterial luminescence associated with the spoilage of marine fish from the Mediterranean-Sea was studied during storage at different temperatures. The bioluminescence level of the bacterial suspensions that were taken from the fish skin increased during the storage; at 20°–25°C the growth and luminescence of the luminuous bacteria correlated well with the total bacterial count while at 5°C the bacterial proliferation was not accompanied by a parallel increase in luminescence.The shift in storage temperature from 25°C to 5°C stabilized the level of the luminescence of bacterial suspension taken from the winter fish which were comprised mainly by Photobacterium phosphoreum, and caused a drop in the luminescence of bacterial suspension taken from the fish caught in the summer which were comprised mainly by Beneckea barveyi. The increase in the bioluminescence level appeared earlier than the increase in trimethylamine level and occured approximately at the same time as the increase in the hypoxanthine concentration. The potential value of the use of bacterial bioluminescence as an early indication for marine fish spoilage is discussed.     

Metabarcoding of PalEnDNA as An Efficient Tool to Recover Ancient Bacterial Diversity

Past bacterial diversity of a paleosol was reconstructed using metabarcoding of paleo environmental DNA (PalEnDNA). The paleosol was subsampled from a sediment core which was excavated from a palaeo beach-ridge located 2.6?km away from present sea shore and identified that it was deposited under marine influence ～6000?years ago, using geological proxies. The bacterial community contained 37 bacterial phyla and dominated by Proteobacteria, followed by Bacteroidetes, Firmicutes, Actinobacteria, Verrucomicrobia, and Chloroflexi. The bacterial community was a mix-up of marine and terrestrial population, and thereby diversity was higher than marine populations. The result shows metabarcoding of PalEnDNA can effectively reconstruct past bacterial community structure.     

Ungeremine effectively targets mammalian as well as bacterial type I and type II topoisomerases

From the methanol extract of the bulbs of Pancratium illyricum L., three phenanthridine type alkaloids, ungeremine (1), (-)-lycorine (2) and (+)-vittatine (3) were isolated. For the evaluation of their anticancer and antibacterial potential, compounds 1-3 were tested against human (I, IIα) and bacterial (IA, IV) topoisomerases. Our data demonstrated that ungeremine impairs the activity of both, human and bacterial topoisomerases. Remarkably, ungeremine was found to largely increments the DNA cleavage promoted by bacterial topoisomerase IA, a new target in antimicrobial chemotherapy.     

Frequency of Dividing Cells as an Estimator of Bacterial Productivity

It has recently been proposed that the frequency of dividing bacterial cells (FDC) can be used to predict growth rates of natural aquatic bacterial assemblages. We have examined the relationship between FDC and growth rate in bacteria from southern-temperate, coastal marine waters by using incubation under conditions of manipulated nutrient availability and exclusion of bacterivores. The regression of the natural logarithm of bacterial instantaneous growth rate (μ) on FDC resulted in a better fit than regression of untransformed μ on FDC. The regression equation was ln μ = 0.299FDC − 4.961. The coefficient of variation for predicted ln μ at mean FDC was 7%. The range of FDC-estimated bacterial instantaneous generation times for coastal Georgia waters was 12 to 68 h, and range of calculated bacterial production rates was 0.6 to 17.6 mg of C·m⁻³· h⁻¹. Unresolved problems of and suggested improvements on the FDC method of predicting growth rate are discussed.     

Phage as agents of lateral gene transfer

When establishing lysogeny, temperate phages integrate their genome as a prophage into the bacterial chromosome. Prophages thus constitute in many bacteria a substantial part of laterally acquired DNA. Some prophages contribute lysogenic conversion genes that are of selective advantage to the bacterial host. Occasionally, phages are also involved in the lateral transfer of other mobile DNA elements or bacterial DNA. Recent advances in the field of genomics have revealed a major impact by phages on bacterial chromosome evolution.     

Evaluation of infrared spectroscopy as a bacterial identification method

Summary A study motivated by the recent revival of interest in the use of IR spectroscopy to identify bacteria is reported. A library of FT-IR spectra of dried bacterial films was compled using 16 different strains. A test set was complied from spectra of the same strains grown several months later. The test set was quantitatively compared with the library on the basis of spectral similarity in the region 980–1190 cm^–1. Six of the strains in the test set were not matched with the correct strain in the library despite efforts to reproduce the conditions under which cells were grown and prepared. The results suggest that reproducibility of the bacterial spectra is a potential difficulty that must be addressed by any attempts to develop FT-IR spectroscopy as a bacterial identification method.     

Human occupancy as a source of indoor airborne bacteria

Exposure to specific airborne bacteria indoors is linked to infectious and noninfectious adverse health outcomes. However, the sources and origins of bacteria suspended in indoor air are not well understood. This study presents evidence for elevated concentrations of indoor airborne bacteria due to human occupancy, and investigates the sources of these bacteria. Samples were collected in a university classroom while occupied and when vacant. The total particle mass concentration, bacterial genome concentration, and bacterial phylogenetic populations were characterized in indoor, outdoor, and ventilation duct supply air, as well as in the dust of ventilation system filters and in floor dust. Occupancy increased the total aerosol mass and bacterial genome concentration in indoor air PM(10) and PM(2.5) size fractions, with an increase of nearly two orders of magnitude in airborne bacterial genome concentration in PM(10). On a per mass basis, floor dust was enriched in bacterial genomes compared to airborne particles. Quantitative comparisons between bacterial populations in indoor air and potential sources suggest that resuspended floor dust is an important contributor to bacterial aerosol populations during occupancy. Experiments that controlled for resuspension from the floor implies that direct human shedding may also significantly impact the concentration of indoor airborne particles. The high content of bacteria specific to the skin, nostrils, and hair of humans found in indoor air and in floor dust indicates that floors are an important reservoir of human-associated bacteria, and that the direct particle shedding of desquamated skin cells and their subsequent resuspension strongly influenced the airborne bacteria population structure in this human-occupied environment. Inhalation exposure to microbes shed by other current or previous human occupants may occur in communal indoor environments.     

Escherichia coli minicells with targeted enzymes as bioreactors for producing toxic compounds

Formed by aberrant cell division, minicells possess functional metabolism despite their inability to grow and divide. Minicells exhibit not only superior stability when compared with bacterial cells but also exceptional tolerance—characteristics that are essential for a de novo bioreactor platform. Accordingly, we engineered minicells to accumulate protein, ensuring sufficient production capability. When tested with chemicals regarded as toxic against cells, the engineered minicells produced titers of C6–C10 alcohols and esters, far surpassing the corresponding production from bacterial cells. Additionally, microbial autoinducer production that is limited in expanding bacterial population was conducted in the minicells. Because bacterial population growth was nonexistent, the minicells produced autoinducers in constant amounts, which allowed precise control of the bacterial population having autoinducer-responsive gene circuits. When bacterial population growth was nonexistent, the minicells produced autoinducers in constant amounts, which allowed precise control of the bacterial population having autoinducer-based gene circuits with the minicells. This study demonstrates the potential of minicells as bioreactors suitable for products with known limitations in microbial production, thus providing new possibilities for bioreactor engineering.     

Composition of Acridid gut bacterial communities as revealed by 16S rRNA gene analysis

The gut bacterial community from four species of feral locusts and grasshoppers was determined by denaturing gradient gel electrophoresis (DGGE) analysis of bacterial 16S rRNA gene fragments. The study revealed an effect of phase polymorphism on gut bacterial diversity in brown locusts from South Africa. A single bacterial phylotype, consistent with Citrobacter sp. dominated the gut microbiota of two sympatric populations of Moroccan and Italian locusts in Spain. There was evidence for Wollbachia sp. in the meadow grasshopper caught locally in the UK. Sequence analysis of DGGE products did not reveal evidence for unculturable bacteria and homologies suggested that bacterial species were principally Gammaproteobacteria from the family Enterobacteriaceae similar to those recorded previously in laboratory reared locusts.     

Evaluation of the Extract-Release Volume Phenomenon as a Rapid Test for Detecting Spoilage in Beef

Ground beef of several grades, obtained fresh and held refrigerated until spoiled, was presented to a test panel for scoring on color, odor, and tactile response (tackiness) as to degree of acceptance. Panel scores were correlated with total bacterial counts, ninhydrin-reactive substances, and ERV (extract-release volume) on the same meat. ERV correlated highest with bacterial counts the largest number of times; tackiness, odor, ninhydrin, and color followed in that order. Correlation between bacterial numbers and organoleptic qualities was best, with tackiness followed closely by odor, and then by color. Correlation between tackiness and odor was high. The degree of correlation between bacterial numbers, tackiness, and ERV was high enough to warrant the use of the ERV phenomenon as a rapid test of microbial quality of beef. An ERV value of 25 under the conditions of the test was supported as a divider between acceptable and unacceptable ground beef.     

Synthetic analogues of SB-219383. Novel C-glycosyl peptides as inhibitors of tyrosyl tRNA synthetase

Novel inhibitors of bacterial tyrosyl tRNA synthetase have been synthesised in which the cyclic hydroxylamine moiety of SB-219383 is replaced by C-pyranosyl derivatives. Potent and selective inhibition of bacterial tyrosyl tRNA synthetase was obtained.     

Neutrophil extracellular traps contain mitochondrial as well as nuclear DNA and exhibit inflammatory potential

Neutrophils expel extracellular traps (NETs) to entrap and exterminate the invaded micro-organisms. Acute/chronic inflammatory disorders are often observed with aberrantly enhanced NETs formation and high nitric oxide (NO) availability. Recent study from this laboratory demonstrated release of NETs from human neutrophils following treatment with SNP or SNAP. This study is an extension of our previous finding to explore the extracellular bacterial killing, source of DNA in the expelled NETs, their ability to induce proinflammatory cytokines release from platelets/THP-1 cells, and assessment of NO-mediated free radical formation by using a consistent NO donor, DETA-NONOate. NO-mediated NETs exhibited extracellular bacterial killing as determined by colony forming units. NO-mediated NETs formation was due to the activation of NADPH oxidase and myeloperoxidase. NO- or PMA-mediated NETs were positive for both nuclear and mitochondrial DNA as well as proteolytic enzymes. Incubation of NETs with human platelets enhanced the release of IL-1β and IL-8, while with THP-1 cells, release of IL-1β, IL-8, and TNFα was observed. This study demonstrates that NO by augmenting enzymatic free radical generation release NETs to promote extracellular bacterial killing. These NETs were made up of mitochondrial and nuclear DNA and potentiated release of proinflammatory cytokines.     

N-glycosyl-N-hydroxysulfamides as potent inhibitors of Brucella suis carbonic anhydrases

Abstract

We investigated a series of N-hydroxysulfamides obtained by Ferrier sulfamidoglycosylation for the inhibition of two bacterial carbonic anhydrases (CAs, EC 4.2.1.1) present in the pathogen Brucella suis. bsCA I was moderately inhibited by these compounds with inhibition constants ranging between 522 and 958?nM and no notable differences of activity between the acetylated or the corresponding deacetylated derivatives. The compounds incorporating two trans-acetates and the corresponding deprotected ones were the most effective inhibitors in the series. bsCA II was better inhibited, with inhibition constants ranging between 59.8 and 799?nM. The acetylated derivatives were generally better bsCA II inhibitors compared to the corresponding deacetylated compounds. Although these compounds were not highly isoform-selective CA inhibitors (CAIs) for the bacterial over the human CA isoforms, some of them possess inhibition profiles that make them interesting leads for obtaining better and more isoform-selective CAIs targeting bacterial enzymes.     

The prokaryotic community of a historically mining-impacted tropical stream sediment is as diverse as that from a pristine stream sediment

Mining negatively affects the environment by producing large quantities of metallic tailings, such as those contaminated with arsenic, with harmful consequences for human and aquatic life. A culture-independent molecular analysis was performed to assess the prokaryotic diversity and community structural changes of the tropical historically metal-contaminated Mina stream (MS) and the relatively pristine Mutuca stream (MTS) sediments. A total of 234 bacterial operational taxonomic units (OTUs) were affiliated with 14 (MS) and 17 (MTS) phyla and 53 OTUs were associated with two archaeal phyla. Although the bacterial community compositions of these sediments were markedly distinct, no significant difference in the diversity indices between the bacterial communities was observed. Additionally, the rarefaction and diversity indices indicated a higher bacterial diversity than archaeal diversity. Most of the OTUs were affiliated with the Proteobacteria and Bacteroidetes phyla. Alphaproteobacteria, Gemmatimonadetes and Actinobacteria were only found in the MS clone library. Crenarchaeal 16S rDNA sequences constituted 75 % of the MS archaeal clones, whereas Euryarchaeota were dominant in the MTS clones. Despite the markedly different characteristics of these streams, their bacterial communities harbor high diversity, suggesting that historically mining-impacted sediments promote diversity. The findings also provide basis for further investigation of members of Alphaproteobacteria as potential biological indicators of arsenic-rich sediments.     

Significance of viral lysis and flagellate grazing as factors controlling bacterioplankton production in a eutrophic lake

The effects of viral lysis and heterotrophic nanoflagellate (HNF) grazing on bacterial mortality were estimated in a eutrophic lake (Lake Plusssee in northern Germany) which was separated by a steep temperature and oxygen gradient into a warm and oxic epilimnion and a cold and anoxic hypolimnion. Two transmission electron microscopy-based methods (whole-cell examination and thin sections) were used to determine the frequency of visibly infected cells, and a model was used to estimate bacterial mortality due to viral lysis. Examination of thin sections also showed that between 20.2 and 29.2% (average, 26.1%) of the bacterial cells were empty (ghosts) and thus could not contribute to viral production. The most important finding was that the mechanism for regulating bacterial production shifted with depth from grazing control in the epilimnion to control due to viral lysis in the hypolimnion. We estimated that in the epilimnion viral lysis accounted on average for 8.4 to 41.8% of the summed mortality (calculated by determining the sum of the mortalities due to lysis and grazing), compared to 51.3 to 91.0% of the summed mortality in the metalimninon and 88.5 to 94.2% of the summed mortality in the hypolimnion. Estimates of summed mortality values indicated that bacterial production was controlled completely or almost completely in the epilimnion (summed mortality, 66.6 to 128.5%) and the hypolimnion (summed mortality, 43.4 to 103.3%), whereas in the metalimnion viral lysis and HNF grazing were not sufficient to control bacterial production (summed mortality, 22.4 to 56.7%). The estimated contribution of organic matter released by viral lysis of cells into the pool of dissolved organic matter (DOM) was low; however, since cell lysis products are very likely labile compared to the bulk DOM, they might stimulate bacterial production. The high mortality of bacterioplankton due to viral lysis in anoxic water indicates that a significant portion of bacterial production in the metalimnion and hypolimnion is cycled in the bacterium-virus-DOM loop. This finding has major implications for the fate and cycling of organic nutrients in lakes.     

Division and death rates of Salmonella typhimurium inside macrophages: use of penicillin as a probe.

In mouse peritoneal macrophages infected in vitro with Salmonella typhimurium the number of viable bacteria and the number of stainable bacteria detected by light microscopy both increased at similar rates with a doubling time of more than 1 h. Antibiotics were not present; instead extracellular bacteria were removed by frequently rinsing the cells. The bacterial doubling time in the same medium in the absence of macrophages was about 20 min. Penicillin added to macrophage monolayers rapidly entered the macrophages, reaching a diffusion equilibrium. The penicillin-induced bacterial death rate appeared to depend on the bacterial division rate as well as on the penicillin concentration. These properties of penicillin were used to monitor intracellular bacterial division and death rates. The results indicated that intracellular killing, with the disappearance of stainable bacteria, did not contribute to the extended doubling time in macrophages. It was concluded that the intracellular environment of the bacteria was probably growth inhibitory but not bactericidal.     

Protein aggregation as an antibiotic design strategy

Taking advantage of the xenobiotic nature of bacterial infections, we tested whether the cytotoxicity of protein aggregation can be targeted to bacterial pathogens without affecting their mammalian hosts. In particular, we examined if peptides encoding aggregation‐prone sequence segments of bacterial proteins can display antimicrobial activity by initiating toxic protein aggregation in bacteria, but not in mammalian cells. Unbiased in vitro screening of aggregating peptide sequences from bacterial genomes lead to the identification of several peptides that are strongly bactericidal against methicillin‐resistant Staphylococcus aureus. Upon parenteral administration in vivo, the peptides cured mice from bacterial sepsis without apparent toxic side effects as judged from histological and hematological evaluation. We found that the peptides enter and accumulate in the bacterial cytosol where they cause aggregation of bacterial polypeptides. Although the precise chain of events that leads to cell death remains to be elucidated, the ability to tap into aggregation‐prone sequences of bacterial proteomes to elicit antimicrobial activity represents a rich and unexplored chemical space to be mined in search of novel therapeutic strategies to fight infectious diseases.     

Increased production of bacterial cellulose as starting point for scaled-up applications

Bacterial cellulose is composed of an ultrafine nanofiber network and well-ordered structure; therefore, it offers several advantages when used as native polymer or in composite systems.

In this study, a pool of 34 acetic acid bacteria strains belonging to Komagataeibacter xylinus were screened for their ability to produce bacterial cellulose. Bacterial cellulose layers of different thickness were observed for all the culture strains. A high-producing strain, which secreted more than 23 g/L of bacterial cellulose on the isolation broth during 10 days of static cultivation, was selected and tested in optimized culture conditions. In static conditions, the increase of cellulose yield and the reduction of by-products such as gluconic acid were observed. Dried bacterial cellulose obtained in the optimized broth was characterized to determine its microstructural, thermal, and mechanical properties. All the findings of this study support the use of bacterial cellulose produced by the selected strain for biomedical and food applications.

     

The structure of bacterial communities in the western Arctic Ocean as revealed by pyrosequencing of 16S rRNA genes

Bacterial communities in the surface layer of the oceans consist of a few abundant phylotypes and many rare ones, most with unknown ecological functions and unclear roles in biogeochemical processes. To test hypotheses about relationships between abundant and rare phylotypes, we examined bacterial communities in the western Arctic Ocean using pyrosequence data of the V6 region of the 16S rRNA gene. Samples were collected from various locations in the Chukchi Sea, the Beaufort Sea and Franklin Bay in summer and winter. We found that bacterial communities differed between summer and winter at a few locations, but overall there was no significant difference between the two seasons in spite of large differences in biogeochemical properties. The sequence data suggested that abundant phylotypes remained abundant while rare phylotypes remained rare between the two seasons and among the Arctic regions examined here, arguing against the ‘seed bank’ hypothesis. Phylotype richness was calculated for various bacterial groups defined by sequence similarity or by phylogeny (phyla and proteobacterial classes). Abundant bacterial groups had higher within‐group diversity than rare groups, suggesting that the ecological success of a bacterial lineage depends on diversity rather than on the dominance of a few phylotypes. In these Arctic waters, in spite of dramatic variation in several biogeochemical properties, bacterial community structure was remarkably stable over time and among regions, and any variation was due to the abundant phylotypes rather than rare ones.