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1.
The present study deals with immobilization of purified CA and whole cell of Pseudomonas fragi, Micrococcus lylae, and Micrococcus luteus 2 on different biopolymer matrices. Highest enzyme immobilization was achieved with P. fragi CA (89%) on chitosan-KOH beads, while maximum cell immobilization was achieved with M. lylae (75%) on chitosan-NH(4)OH beads. A maximum increase of 1.08-1.18 fold stability between 35 and 55°C was observed for M. lylae immobilized CA. The storage stability was improved by 2.02 folds after immobilization. FTIR spectra confirmed the adsorption of CA on chitosan-KOH beads following hydrophilic interactions. Calcium carbonate precipitation was achieved using chitosan-KOH immobilized P. fragi CA. More than 2 fold increase in sequestration potential was observed for immobilized system as compared to free enzyme. XRD spectra revealed calcite as the dominant phase in biomimetically produced calcium carbonate.  相似文献   

2.
Seventy strains of Staphylococcus spp. and Escherichia coli (35 each) were isolated from various foodstuffs and identified on the basis of cultural, morphological and biochemical characteristics and were further tested for their antibiotic susceptibility with commonly used antibiotics/drugs. 69.2% of the strains of Staphylococci were resistant to co-trimazine and 34.6% were resistant to penicillin-G. 19.2% of the staphylococcal isolates exhibited resistance to cloxacillin, nalidixic acid, methicillin and tetracycline whereas 15.3% of the staphylococcal isolates were resistant to amoxycillin and nitrofurantoin. The isolated E. coli strains exhibited sharp peaks of resistance to antimicrobial agents such as tetracycline (72%), doxycycline (60%) and nalidixic acid (48%). Forty-four percent of the E. coli strains were resistant to nitrofurantoin and penicillin-G respectively. Among the 13 antibiotics/drugs tested for resistance, six different resistance patterns were observed in staphylococcal isolates and seven different resistance patterns were observed in the E. coli isolates from various foodstuffs. Bacterial strains exhibiting MIC values 100 g/ml for ampicillin and cloxacillin were screened for -lactamase activity and out of 10 staphylococcal isolates, seven were found to be positive for -lactamase, whereas out of 13 E. coli isolates tested for -lactamase production, only three were found to be positive.  相似文献   

3.
Abstract

This study investigated how the physiological states of Aggregatibacter actinomycetemcomitans (Aa) and Streptococcus mitis affect their intracellular invasion capabilities and the resulting host cell responses. The physiological states included two forms of planktonic states, floating or sedimented (by centrifugation) and the biofilm state (with centrifugation). Confluent epithelial Ca9-22 cells were challenged with floating or sedimented planktonic cultures, or with 24-h biofilms for 3?h. The results show that intracellular invasion efficiencies were clearly affected by the bacterial physiological states. For both bacterial species, the sedimented-cells displayed 2–10 times higher invasion efficiency than the floating-cells (p?<?0.05). The invasion efficiency of Aa biofilms was three fold lower than sedimented cells, whereas those of S. mitis biofilms were similar to sedimented cells. Unlike invasion, the metabolic activities of Ca9-22 were unaffected by different bacterial physiological states. However, Aa biofilms induced higher IL-1β expression than planktonic cultures. In conclusion, different bacterial physiological states can affect the outcomes of (in vitro) host–microbe interaction in different ways.  相似文献   

4.
5.
Can bacterial interference prevent infection?   总被引:11,自引:0,他引:11  
The concept that one bacterial species can interfere with the ability of another to colonize and infect the host has at its foundation the prerequisite that bacteria must attach to biological surfaces to cause infection. Although this is an over-simplification of pathogenesis, it has led to studies aimed at creating vaccines that block adhesion events. Arguably, the use of commensal bacteria (also referred to as "normal flora", "indigenous" or "autochthonous" microorganisms) to inhibit pathogens has even greater potential than vaccine use, because these bacteria are natural competitors of pathogens and their action does not require host immune stimulation. Exogenous application of commensal organisms (probiotics) has been shown to reduce the risk of infections in the gut, urogenital tract and wound sites. To manipulate and optimize these effects, further studies are required to understand cell signaling amongst commensals and pathogens within biofilms adherent to host tissues. The potential for new therapeutic regimens using probiotics is significant and worthy of further study.  相似文献   

6.
Attempts to control bacterial pathogens have led to an increase in antibiotic-resistant cells and the genetic elements that confer resistance phenotypes. These cells and genes are disseminated simultaneously with the original selective agents via human waste streams. This might lead to a second, unintended consequence of antimicrobial therapy; an increase in the evolvability of all bacterial cells. The genetic variation upon which natural selection acts is a consequence of mutation, recombination and lateral gene transfer (LGT). These processes are under selection, balancing genomic integrity against the advantages accrued by genetic innovation. Saturation of the environment with selective agents might cause directional selection for higher rates of mutation, recombination and LGT, producing unpredictable consequences for humans and the biosphere.  相似文献   

7.
8.

Bacterial vaginosis (BV) has been described as a disease, a disorder, a vaginal inflammation, an infection, a microbial dysbiosis, a condition, and in some women, a normal situation. In order to fit the definition of a disease, BV would have to be a disorder of function that produces specific signs or symptoms or affects the vagina in an aberrant way. Yet, there is little consistency in patients reporting signs and symptoms when BV is diagnosed, nor the appearance of aberrations to the vagina. If BV is not a disease, there are implications for its management and coverage of treatment costs, and for the conclusions drawn in a multitude of previous studies. It is time for BV to be redefined and for the various subsets to be given a separate terminology with specific methods of diagnosis and appropriate treatment and preventive strategies.

  相似文献   

9.
We established a Chelex 100-Microwave method for the purification of bacterial genomic DNA (gDNA) in less than 20 min with high yield and good quality, useful for multiple purposes. It combines Chelex 100, proteinase K, RNase A and heating in a microwave oven. The resulting gDNA was used directly to identify bacterial species of the Order Lactobacillales by means of PCR amplification of their 16S rDNA gene, isolated from sediments on the Yucatan Peninsula, Mexico. This method produced gDNA free of phenolic and protein residual contaminants from 100 of these isolated bacteria. 16S rDNA amplification and sequencing showed Pediococcus acidilactici to prevail in inland lagoons, and Pediococcus pentosaceus, Lactobacillus plantarum, Lactobacillus sp., and Lactobacillus fermentum to be most abundant in the soils of livestock farms. The combination of Chelex 100, enzymes and microwave heating used in the Chelex 100-Microwave method produced large amounts of highly pure gDNA from Gram-positive and Gram-negative bacteria, in less than 20 min.  相似文献   

10.
The ability of bacteria to evolve resistance to antibiotics has been much reported in recent years. It is less well-known that within populations of bacteria there are cells which are resistant due to a non-inherited phenotypic switch to a slow-growing state. Although such 'persister' cells are receiving increasing attention, the evolutionary forces involved have been relatively ignored. Persistence has a direct benefit to cells because it allows survival during catastrophes-a form of bet-hedging. However, persistence can also provide an indirect benefit to other individuals, because the reduced growth rate can reduce competition for limiting resources. This raises the possibility that persistence is a social trait, which can be influenced by kin selection. We develop a theoretical model to investigate the social consequences of persistence. We predict that selection for persistence is increased when: (a) cells are related (e.g. a single, clonal lineage); and (b) resources are scarce. Our model allows us to predict how the level of persistence should vary with time, across populations, in response to intervention strategies and the level of competition. More generally, our results clarify the links between persistence and other bet-hedging or social behaviours.  相似文献   

11.
Cell—cell interactions in bacterial populations   总被引:5,自引:0,他引:5  
In developing bacterial populations many essential processes, such as division, genetic transformation, sporulation, and synthesis of antibiotics and secondary metabolites, are regulated by intercellular communication mediated by secretion of signaling molecules, such as homoserine lactones and peptides. Another intercellular communication type, namely a physical contact between cells (cell aggregation), plays a key role in formation of biofilms or cellular consortia and in cell proliferation under unfavorable conditions. The mechanisms involved in these two types of bacterial communication are discussed in this review.Translated from Biokhimiya, Vol. 69, No. 11, 2004, pp. 1555–1564.Original Russian Text Copyright © 2004 by Voloshin, Kaprelyants  相似文献   

12.
13.
Toxin–antitoxin (TA) systems are widespread in bacteria and archaea and play important roles in a diverse range of cellular activities. TA systems have been broadly classified into 5 types and the targets of the toxins are diverse, but the most frequently used cellular target is mRNA. Toxins that target mRNA to inhibit translation can be classified as ribosome-dependent or ribosome-independent RNA interferases. These RNA interferases are sequence-specific endoribonucleases that cleave RNA at specific sequences. Despite limited sequence similarity, ribosome-independent RNA interferases belong to a limited number of structural classes. The MazF structural family includes MazF, Kid, ParE and CcdB toxins. MazF members cleave mRNA at 3-, 5- or 7-base recognition sequences in different bacteria and have been implicated in controlling cell death (programmed) and cell growth, and cellular responses to nutrient starvation, antibiotics, heat and oxidative stress. VapC endoribonucleases belong to the PIN-domain family and inhibit translation by either cleaving tRNAfMet in the anticodon stem loop, cleaving mRNA at -AUA(U/A)-hairpin-G- sequences or by sequence-specific RNA binding. VapC has been implicated in controlling bacterial growth in the intracellular environment and in microbial adaptation to nutrient limitation (nitrogen, carbon) and heat shock. ToxN shows structural homology to MazF and is also a sequence-specific endoribonuclease. ToxN confers phage resistance by causing cell death upon phage infection by cleaving cellular and phage RNAs, thereby interfering with bacterial and phage growth. Notwithstanding our recent progress in understanding ribonuclease action and function in TA systems, the environmental triggers that cause release of the toxin from its cognate antitoxin and the precise cellular function of these systems in many bacteria remain to be discovered. This article is part of a Special Issue entitled: RNA Decay mechanisms.  相似文献   

14.
Summary Fragments ofEscherichia coli DNA carrying genes for -galactosidase, or for biosynthesis of guanine or biotin were recombined in vitro with dv DNA. The cloned recombinant molecules recovered from transformedE. coli cells consisted of a biologically functional bacterial DNA fragment and, except for dv-bio30-7, two dv monomer units: one of the dv units was used as the insertion site for the bacterial DNA, whereas the other was intact, and seemed to be responsible for the replication of the recombinant plasmid. The process which gives rise to these recombinant molecules at high frequency from mixtures of monomeric dv DNA's and bacterial DNA fragments is discussed.  相似文献   

15.
The application potential of microfungal strains (Cadophora malorum, Mucor circinelloides, Trichoderma viride, nonsporulating culture Mycelia sterilia) as promising lipid producers is investigated. The C. malorum strain is found to be optimal for oil sludge recycling into biofuel. Its palmitic acid content is 52.9%, and it ensures a cetane number of the obtained biodiesel. The ability of the C. malorum strain to degrade n-alkanes and polyaromatic hydrocarbons allows the effective bioremediation of oil sludge to be performed.  相似文献   

16.
Summary A constitutive -galactosidase has been localized in the cytosol of thermoacidophilic bacterium Caldariella acidophila. Cells have been entrapped in polyacrylamide gel with full retention of enzymic activity; no activity decrease is observed after 8 months of storage. Enzyme properties in entrapped cells are similar to those of the free enzyme. A 73% hydrolysis of lactose has been achieved in a continuous system on a 2 ml entrapped cell column operating at 70°C; half life in these conditions is 30 days.In this paper we report preliminary data on immobilization of cells of Caldariella acidophila, an extreme thermophilic bacterium having a constitutive -galactosidase (EC 3.2.1.23) activity.  相似文献   

17.
Walk into any field and you will at once see dozens of plant and animal species. However, below your feet and largely unnoticed, lies a population of unseen millions. Can the introduction of powerful molecular biological techniques increase our understanding of how these hidden bacterial communities function in their natural environment?  相似文献   

18.
Are bacterial ‘autotransporters’ really transporters?   总被引:1,自引:0,他引:1  
Autotransporters are bacterial outer membrane proteins that consist of a large N-terminal extracellular domain ('passenger domain') and a C-terminal beta-barrel domain ('beta domain'). The beta domain was originally proposed to function as a channel that transports its own passenger domain across the outer membrane. Results of recent structural, biochemical and molecular genetic studies, however, have challenged this idea. Here I describe an alternative model in which translocation of the passenger domain is mediated by an exogenous factor (possibly a newly identified factor necessary for assembly of outer membrane proteins called 'Omp85/YaeT'), whereas the beta domain only targets the protein to the outer membrane and serves as a membrane anchor.  相似文献   

19.
The properties and application of l-methionine γ-lyase [methioninase, l-methionine methanethiol-lyase (deaminating), EC 4.4.1.11], a pyridoxal 5′-phosphate enzyme, purified from Pseudomonas putida and Aeromonas sp. are presented. The enzyme has multicatalytic functions: it catalyses α,γ-elimination and γ-replacement reactions of l-methionine and its analogues (e.g. ethionine, homocysteine, O-acetylhomoserine and selenomethionine), α,β-elimination and β-replacement reactions of l-cysteine and its analogues (e.g. S-methylcysteine, O-acetylserine and Se-methylselenocysteine), deamination and γ-addition of vinylglycine, and deuterium labelling at the α and β positions of l-methionine and other straight-chain l-amino acids. These reactions are applicable to the synthesis of various optically active sulphur and selenium amino acids, preparation of deuterium or tritium labelled l-amino acids, and determination of sulphur amino acids. In addition, the enzyme shows potent anti-neoplastic activity.  相似文献   

20.
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