Operon Research Articles

Prevalence and virulence factors of coagulase negative Staphylococcus causative of prosthetic joint infections in an orthopedic hospital of Mexico.

To determine the prevalence and virulence factors of coagulase-negative Staphylococci (CNS) in prosthetic joint infections (PJI). CNS were isolated of 66 hip and knee PJI from Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, México City. Antimicrobial susceptibility and biofilm formation in CNS were determined; icaADBC, aap, bap and embp genes were determined by PCR. Staphylococcus and Staphylococcus hominis were the most prevalent with 82 y 80% respectively. Staphylococcus lugdunensis, Staphylococcus haemolyticus, Staphylococcus capitis, Staphylococcus caprae, Staphylococcus sciuri and Staphylococcus lentus were less frequent. The majority of isolates were resistant to β-lactam antibiotics, fluoroquinolone, and erythromycin. 41% of CNS were biofilm former and 59% were non-biofilm former (p = 0.0551). Biofilm former Staphylococcus epidermidis showed a high presence of icaADBC, aap and embp operons compared to the non-biofilm former isolates (p < 0.05). In contrast, non-S. epidermidis CNS had only the aap gen. S. haemolyticus, S. sciuri and S. lentus are new isolates of PJI not previously reported with virulence factors similar to CNS isolates.

Isolation and Molecular Identification of Arsenic Resistant Microorganisms Coming from Xichu River, Gto. Mexico.

The arsenic is a toxic element for the human and other organisms´ health, it may affect the exploitation of water, the agriculture development and the sustainable rational use of soil, the result is reflected within the socioeconomic growth lag in the affected area. Arsenic is mobilized in the environment by a combination of several natural processes, such as weathering reactions, biological activities and volcanic emissions, as well as by a group of anthropogenic activities. Microorganisms interact with the arsenic through a different mechanism such as adsorption, redox, precipitation, etc. On the other hand, the rate of arsenic releasing in geochemical environments is controlled mainly by microorganisms. In the environment, the major arsenic transformations include microbial oxidation, reduction, methylation and demethylation, those reactions have an enormous impact in the arsenic behavior that depends on its redox state that exhibits differences in its mobility and toxicity. Normally, the arsenic resistance comes through the production of genes within operon ars, their location is usually plasmid or chromosomic. In this study, it was achieved the isolation of 11 strains from which 2 have been reported as an arsenic resistant in this work. The samples were collected from water, sediment and biofilm of Xichu River, which has been impacted by mining activity, exhibiting a high arsenic concentration (98 µg/l). All the strains were tested by several methods as arsenic resistance, colorimetric test for arsenate reduction, pDNA extraction as well as ars and aox genes amplification, which are the genes involved in arsenic transformation. It was obtained a great microbial diversity with different skills in arsenic transformation. One of the isolated strains Rodoccoccus gordoniae, did not show the presence of any gen but it was the most likely microorganisms to grow in the presence of arsenic. Almost all the microorganisms showed arsenic resistant until 20 mM of arsenite and arsenate. The main contribution of this study is the development of knowledge to understand much better the arsenic biogeochemistry, as well as the development of new bio-technologies for water treatment in rural communities impacted by mining activity.

Multifaceted Stoichiometry Control of Bacterial Operons Revealed by Deep Proteome Quantification.

More than half of the protein-coding genes in bacteria are organized in polycistronic operons composed of two or more genes. It remains under debate whether the operon organization maintains the stoichiometric expression of the genes within an operon. In this study, we performed a label-free data-independent acquisition hyper reaction monitoring mass-spectrometry (HRM-MS) experiment to quantify the Escherichia coli proteome in exponential phase and quantified 93.6% of the cytosolic proteins, covering 67.9% and 56.0% of the translating polycistronic operons in BW25113 and MG1655 strains, respectively. We found that the translational regulation contributes largely to the proteome complexity: the shorter operons tend to be more tightly controlled for stoichiometry than longer operons; the operons which mainly code for complexes is more tightly controlled for stoichiometry than the operons which mainly code for metabolic pathways. The gene interval (distance between adjacent genes in one operon) may serve as a regulatory factor for stoichiometry. The catalytic efficiency might be a driving force for differential expression of enzymes encoded in one operon. These results illustrated the multifaceted nature of the operon regulation: the operon unified transcriptional level and gene-specific translational level. This multi-level regulation benefits the host by optimizing the efficiency of the productivity of metabolic pathways and maintenance of different types of protein complexes.

Identification of the two-component guaiacol demethylase system from Rhodococcus rhodochrous and expression in Pseudomonas putida EM42 for guaiacol assimilation

A diversity of softwood lignin depolymerization processes yield guaiacol as the main low molecular weight product. This key aromatic compound can be utilized as a carbon source by several microbial species, most of which are Gram positive bacteria. Microbial degradation of guaiacol is known to proceed initially via demethylation to catechol, and this reaction is catalyzed by cytochrome P450 monooxygenases. These enzymes typically require a set of redox partner proteins, whose number and identities were not described until very recently in the case of guaiacol. In this work we identified two proteins involved in guaiacol demethylation by the actinomycete Rhodococcus rhodochrous. Additionally, we constructed four different polycistronic operons carrying combinations of putative redox partners of this guaiacol demethylation system in an inducible expression plasmid that was introduced into the Gram negative host Pseudomonas putida EM42, and the guaiacol consumption dynamics of each resulting strain were analyzed. All the polycistronic operons, expressing a cytochrome P450 together with a putative ferredoxin reductase from R. rhodochrous and putative ferredoxins from R. rhodochrous or Amycolatopsis ATCC 39116 enabled P. putida EM42 to metabolize and grow on guaiacol as the sole carbon source.

IMPROVEMENT OF THE METHODOLOGY OF AUDIT OF OPERATIONS ON BUDGET ACCOUNTS OF ENTERPRISES

IMPROVEMENT OF THE METHODOLOGY OF AUDIT OF OPERATIONS ON BUDGET ACCOUNTS OF ENTERPRISES

Correction: Rv1460, a SufR homologue, is a repressor of the suf operon in Mycobacterium tuberculosis.

[This corrects the article DOI: 10.1371/journal.pone.0200145.].

Complete genome of Bacillussubtilis subsp. subtilis KCTC 3135T and variation in cell wall genes of B. subtilis strains.

The type strain Bacillus subtilis subsp.subtilis KCTC 3135T was deeply sequenced and annotated, replacing a previous draft genome in this study. The tar and tag genes were involved in synthesizing wall teichoic acids (WTAs), and these genes and their products were previously regarded as the distinguishing difference between B. s. subtilis and B. s. spizizenii. However, a comparative genomic analysis of B. subtilis spp. revealed that both B. s. subtilis and B. s. spizizenii had various types of cell walls. These tar and tag operons were mutually exclusive and the tar genes from B. s. spizizenii were very similar to the genes from non-Bacillus bacteria, unlike the tag genes from B. s. subtilis. The results and previous studies suggests that the tar genes and the tag genes are not inherited after subspecies speciation. The phylogenetic tree based on whole genome sequences showed that each subspecies clearly formed a monophyletic group, while the tree based on tar genes showed that monophyletic groups were formed according to the cell wall type rather than the subspecies. These findings indicate that the tar genes and the presence of ribitol as a cell-wall constituent were not the distinguishing difference between the subspecies of B. subtilis and that the description of subspecies B. s. spizizenii should be updated.

A Light-Regulated Type I Pilus Contributes to Acinetobacter baumannii Biofilm, Motility, and Virulence Functions.

Transcriptional analyses of Acinetobacter baumannii ATCC 17978 showed that the expression of A1S_2091 was enhanced in cells cultured in darkness at 24°C through a process that depended on the BlsA photoreceptor. Disruption of A1S_2091, a component of the A1S_2088-A1S_2091 polycistronic operon predicted to code for a type I chaperone/usher pilus assembly system, abolished surface motility and pellicle formation but significantly enhanced biofilm formation on plastic by bacteria cultured in darkness. Based on these observations, the A1S_2088-A1S_2091 operon was named the photoregulated pilus ABCD (prpABCD) operon, with A1S_2091 coding for the PrpA pilin subunit. Unexpectedly, comparative analyses of ATCC 17978 and prpA isogenic mutant cells cultured at 37°C showed the expression of light-regulated biofilm biogenesis and motility functions under a temperature condition that drastically affects BlsA production and its light-sensing activity. These assays also suggest that ATCC 17978 cells produce alternative light-regulated adhesins and/or pilus systems that enhance bacterial adhesion and biofilm formation at both 24°C and 37°C on plastic as well as on the surface of polarized A549 alveolar epithelial cells, where the formation of bacterial filaments and cell chains was significantly enhanced. The inactivation of prpA also resulted in a significant reduction in virulence when tested by using the Galleria mellonella virulence model. All these observations provide strong evidence showing the capacity of A. baumannii to sense light and interact with biotic and abiotic surfaces using undetermined alternative sensing and regulatory systems as well as alternative adherence and motility cellular functions that allow this pathogen to persist in different ecological niches.

Local Repressor AcrR Regulates AcrAB Efflux Pump Required for Biofilm Formation and Virulence in Acinetobacter nosocomialis.

Multidrug efflux systems contribute to antimicrobial resistance and pathogenicity in bacteria. Here, we report the identification and characterization of a transcriptional regulator AcrR controlling the yet uncharacterized multidrug efflux pump, AcrAB in Acinetobacter nosocomialis. In silico analysis revealed that the homologs of AcrR and AcrAB are reported in the genomes of many other bacterial species. We confirmed that the genes encoding the AcrAB efflux pump, acrA and acrB forms a polycistronic operon which is under the control of acrR gene upstream of acrA. Bioinformatic analysis indicated the presence of AcrR binding motif in the promoter region of acrAB operon and the specific binding of AcrR was confirmed by electrophoretic mobility shift assay (EMSA). The EMSA data showed that AcrR binds to −89 bp upstream of the start codon of acrA. The mRNA expression analysis depicted that the expression of acrA and acrB genes are elevated in the deletion mutant compared to that in the wild type confirming that AcrR acts as a repressor of acrAB operon in A. nosocomialis. The deletion of acrR resulted in increased motility, biofilm/pellicle formation and invasion in A. nosocomialis. We further analyzed the role of AcrR in A. nosocomialis pathogenesis in vivo using murine model and it was shown that acrR mutant is highly virulent inducing severe infection in mouse leading to host death. In addition, the intracellular survival rate of acrR mutant was higher compared to that of wild type. Our data demonstrates that AcrR functions as an important regulator of AcrAB efflux pump and is associated with several phenotypes such as motility, biofilm/pellicle formation and pathogenesis in A. nosocomialis.

Hydrogen-Cycling during Solventogenesis in Clostridium acetobutylicum American Type Culture Collection (ATCC) 824 Requires the [NiFe]-Hydrogenase for Energy Conservation

Clostridium acetobutylicum has traditionally been used for production of acetone, butanol, and ethanol (ABE). Butanol is a commodity chemical due in part to its suitability as a biofuel; however, the current yield of this product from biological systems is not economically feasible as an alternative fuel source. Understanding solvent phase physiology, solvent tolerance, and their genetic underpinning is key for future strain optimization of the bacterium. This study shows the importance of a [NiFe]-hydrogenase in solvent phase physiology. C. acetobutylicum genes ca_c0810 and ca_c0811, annotated as a HypF and HypD maturation factor, were found to be required for [NiFe]-hydrogenase activity. They were shown to be part of a polycistronic operon with other hyp genes. Hydrogenase activity assays of the ΔhypF/hypD mutant showed an almost complete inactivation of the [NiFe]-hydrogenase. Metabolic studies comparing ΔhypF/hypD and wild type (WT) strains in planktonic and sessile conditions indicated the hydrogenase was important for solvent phase metabolism. For the mutant, reabsorption of acetate and butyrate was inhibited during solventogenesis in planktonic cultures, and less ABE was produced. During sessile growth, the ΔhypF/hypD mutant had higher initial acetone: butanol ratios, which is consistent with the inability to obtain reduced cofactors via H2 uptake. In sessile conditions, the ΔhypF/hypD mutant was inhibited in early solventogenesis, but it appeared to remodel its metabolism and produced mainly butanol in late solventogenesis without the uptake of acids. Energy filtered transmission electron microscopy (EFTEM) mapped Pd(II) reduction via [NiFe]-hydrogenase induced H2 oxidation at the extracelluar side of the membrane on WT cells. A decrease of Pd(0) deposits on ΔhypF/hypD comparatively to WT indicates that the [NiFe]-hydrogenase contributed to the Pd(II) reduction. Calculations of reaction potentials during acidogenesis and solventogenesis predict the [NiFe]-hydrogenase can couple NAD+ reduction with membrane transport of electrons. Extracellular oxidation of H2 combined with the potential for electron transport across the membrane indicate that the [NiFe}-hydrogenase contributes to proton motive force maintenance via hydrogen cycling.

Biomimetic strategy for constructing Clostridium thermocellum cellulosomal operons in Bacillus subtilis

BackgroundEnzymatic conversion of lignocellulosic biomass into soluble sugars is a major bottleneck in the plant biomass utilization. Several anaerobic organisms cope these issues via multiple-enzyme complex system so called ‘cellulosome’. Hence, we proposed a “biomimic operon” concept for making an artificial cellulosome which can be used as a promising tool for the expression of cellulosomal enzymes in Bacillus subtilis.ResultsAccording to the proteomic analysis of Clostridium thermocellum ATCC27405 induced by Avicel or cellobiose, we selected eight highly expressed cellulosomal genes including a scaffoldin protein gene (cipA), a cell-surface anchor gene (sdbA), two exoglucanase genes (celK and celS), two endoglucanase genes (celA and celR), and two xylanase genes (xynC and xynZ). Arranging these eight genes in two different orders, we constructed two different polycistronic operons using the ordered gene assembly in Bacillus method. This is the first study to express the whole CipA along with cellulolytic enzymes in B. subtilis. Each operon was successfully expressed in B. subtilis RM125, and the protein complex assembly, cellulose-binding ability, thermostability, and cellulolytic activity were demonstrated. The operon with a higher xylanase activity showed greater saccharification on complex cellulosic substrates such as Napier grass than the other operon.ConclusionsIn this study, a strategy for constructing an efficient cellulosome system was developed and two different artificial cellulosomal operons were constructed. Both operons could efficiently express the cellulosomal enzymes and exhibited cellulose saccharification. This strategy can be applied to different industries with cellulose-containing materials, such as papermaking, biofuel, agricultural compost, mushroom cultivation, and waste processing industries.

System-wide coordinates of higher order functions in host-pathogen environment upon Mycobacterium tuberculosis infection

Molecular signatures and their interactions behind the successful establishment of infection of Mycobacterium tuberculosis (Mtb) inside macrophage are largely unknown. In this work, we present an inter-system scale atlas of the gene expression signatures, their interactions and higher order gene functions of macrophage-Mtb environment at the time of infection. We have carried out large-scale meta-analysis of previously published gene expression microarray studies andhave identified a ranked list of differentially expressed genes and their higher order functions in intracellular Mtb as well as the infected macrophage. Comparative analysis of gene expression signatures of intracellular Mtb with the in vitro dormant Mtb at different hypoxic and oxidative stress conditions led to the identification of the large number of Mtb functional groups, namely operons, regulons and pathways that were common and unique to the intracellular environment and dormancy state. Some of the functions that are specific to intracellular Mtb are cholesterol degradation and biosynthesis of immunomodulatory phenolic compounds. The molecular signatures we have identified to be involved in adaptation to different stress conditions in macrophage environment may be critical for designing therapeutic interventions against tuberculosis. And, our approach may be broadly applicable for investigating other host-pathogen interactions.

EcoFlex: A Multifunctional MoClo Kit for E. coli Synthetic Biology.

Development of advanced synthetic biology tools is always in demand since they act as a platform technology to enable rapid prototyping of biological constructs in a high-throughput manner. EcoFlex is a modular cloning (MoClo) kit for Escherichia coli and is based on the Golden Gate principles, whereby Type IIS restriction enzymes (BsaI, BsmBI, BpiI) are used to construct modular genetic elements (biological parts) in a bottom-up approach. Here, we describe a collection of plasmids that stores various biological parts including promoters, RBSs, terminators, ORFs, and destination vectors, each encoding compatible overhangs allowing hierarchical assembly into single transcription units or a full-length polycistronic operon or biosynthetic pathway. A secondary module cloning site is also available for pathway optimization, in order to limit library size if necessary. Here, we show the utility of EcoFlex using the violacein biosynthesis pathway as an example.

Pathotyping of diarrhoeagenic cattle Escherichia coli strains isolated in the Province of Tehran, Iran.

An oligonucleotide DNA microarray targeting 348 virulence factors and genetic markers was used in the pathotyping, serotyping and phylogrouping of 51 Escherichia coli strains isolated from faecal samples. The samples were collected from diarrhoeic 1 to 30 days old calves located at 14 farms in the Tehran province, Iran. Positive microarray signals for genes encoding the Locus of Enterocyte E acement (LEE), the Type III Secretion System (TTSS), and the absence of EPEC adherence factor (EAF) permitted the pathotyping of 25 strains as atypical Enteropathogenic (aEPEC) or Enterohaemorrhagic Escherichia coli (EHEC). The lack of LEE and TTSS-associated genes distinguished the remaining 26 strains, which were classi ed as Extraintestinal pathogenic E. coli (ExPEC). Atypical EPEC belonged to phylogroup B1 and possessed a LEE pro le tir-1, eae(beta), espA-1, espB-3. The EHEC strains primarily belonged to the B1 phylogroup type-O26 and possessed either a LEE pro le tir-1, eae(beta), espA-1, espB-3, or a B1 type-O111, LEE tir-3, eae(gamma), espA-1, espB-2. ExPEC-typed strains generally harboured genes localised to the constant region of Colicin V plasmid (pColV), including increased serum survival factor (iss), complement resistance protein (traT), aerobactin operon (iucD), and the siderophore receptor (iroN). The microarray platform used in this study is well suited to accurately and rapidly type attaching and e acing E. coli (AEEC-types), thus providing a database for the meta-analysis of ExPEC-typed strains.

UbiGate: a synthetic biology toolbox to analyse ubiquitination.

Ubiquitination is mediated by an enzymatic cascade that results in the modification of substrate proteins, redefining their fate. This post-translational modification is involved in most cellular processes, yet its analysis faces manifold obstacles due to its complex and ubiquitous nature. Reconstitution of the ubiquitination cascade in bacterial systems circumvents several of these problems and was shown to faithfully recapitulate the process. Here, we present UbiGate - a synthetic biology toolbox, together with an inducible bacterial expression system - to enable the straightforward reconstitution of the ubiquitination cascades of different organisms in Escherichia coli by 'Golden Gate' cloning. This inclusive toolbox uses a hierarchical modular cloning system to assemble complex DNA molecules encoding the multiple genetic elements of the ubiquitination cascade in a predefined order, to generate polycistronic operons for expression. We demonstrate the efficiency of UbiGate in generating a variety of expression elements to reconstitute autoubiquitination by different E3 ligases and the modification of their substrates, as well as its usefulness for dissecting the process in a time- and cost-effective manner.

A 14–20 kDa protein binds to the upstream region of the phtM operon involved in the synthesis of phaseolotoxin in Pseudomonas syringae pv. phaseolicola NPS3121

Pseudomonas syringae pv. phaseolicola is a phytopathogenic bacterium in beans that produces a phytotoxin called phaseolotoxin, in whose synthesis a group of genes that belong to the “Pht cluster” are involved. This cluster comprises 23 genes arranged in 5 transcriptional units, two monocistronic (argK, phtL) and three polycistronic (phtA, phtD, phtM) operons, whose expression is increased at 18°C, correlating with the production of phaseolotoxin by the bacterium. So far, the regulatory mechanisms involved in phaseolotoxin synthesis are poorly understood and only the requirement of low temperatures for its synthesis has been demonstrated. Therefore, in this study we searched for regulatory proteins that could be involved in the phaseolotoxin synthesis, focusing on the regulation of the phtM operon. Gel shift assays showed that the promoter region of the phtM operon contains binding sites for putative regulatory proteins, which are encoded outside the Pht cluster and are independent of the GacS–GacA two-component system. Deletion assays with the promoter region of the phtM operon show that the binding site for a putative transcription factor is located within a 58bp region. The putative transcription factor of the phtM operon has an apparent molecular mass in the 14–20kDa range. Furthermore, the results demonstrate that the transcription factor recognizes and binds the upstream phtM region as monomer o multimer of a single polypeptide. Our findings provide new insights into the regulatory mechanisms involved in phaseolotoxin production, and suggest that the Pht cluster was integrated into the global regulatory mechanism of P. syringae pv. phaseolicola.

A New Physiological Role for CcpA in Adaptation of Bacillus Subtilis to Sugar-Induced Osmotic Stress

The model Gram positive bacterium Bacillus subtilis is liable to be exposed to high salinity environments in its natural habitats and is often used in fermentation with high concentrations of glucose or other sugars High salinity or high concentrations of sugars can cause osmotic stress to B subtilis Past researches regarding osmoadaptation of B subtilis were mainly focused on responses to salt induced osmotic stress There was little or no mention about how B subtilis cells responded to sugar induced osmotic stress The catabolite control protein CcpA is known to be a global transcriptional regulator that mediates glucose repression of many catabolic genes and activation of genes involved in excretion of excess carbon in various Bacillus species However the physiological significance for CcpA mediated sugar activation of degU gltAB opuA opuE proHJ and the ilvB operon remained poorly defined Here based on the results from the literature search it is now proposed that CcpA mediated sugar activation of these osmoadaptive genes may facilitate the adaptation of B subtilis to sugar induced osmotic stress This finding could add a new physiological role to CcpA in B subtilis and probably its close relatives As to biotechnological application construction of B subtilis strains that could over express CcpA might potentially enhance their abilities to withstand higher concentrations of sugars for producing higher yields of various economically effective fermentation products

Genome-wide mRNA processing in methanogenic archaea reveals post-transcriptional regulation of ribosomal protein synthesis.

Unlike stable RNAs that require processing for maturation, prokaryotic cellular mRNAs generally follow an ‘all-or-none’ pattern. Herein, we used a 5΄ monophosphate transcript sequencing (5΄P-seq) that specifically captured the 5΄-end of processed transcripts and mapped the genome-wide RNA processing sites (PSSs) in a methanogenic archaeon. Following statistical analysis and stringent filtration, we identified 1429 PSSs, among which 23.5% and 5.4% were located in 5΄ untranslated region (uPSS) and intergenic region (iPSS), respectively. A predominant uridine downstream PSSs served as a processing signature. Remarkably, 5΄P-seq detected overrepresented uPSS and iPSS in the polycistronic operons encoding ribosomal proteins, and the majority upstream and proximal ribosome binding sites, suggesting a regulatory role of processing on translation initiation. The processed transcripts showed increased stability and translation efficiency. Particularly, processing within the tricistronic transcript of rplA-rplJ-rplL enhanced the translation of rplL, which can provide a driving force for the 1:4 stoichiometry of L10 to L12 in the ribosome. Growth-associated mRNA processing intensities were also correlated with the cellular ribosomal protein levels, thereby suggesting that mRNA processing is involved in tuning growth-dependent ribosome synthesis. In conclusion, our findings suggest that mRNA processing-mediated post-transcriptional regulation is a potential mechanism of ribosomal protein synthesis and stoichiometry.

Additional regulatory activities of MrkH for the transcriptional expression of the Klebsiella pneumoniae mrk genes: Antagonist of H-NS and repressor.

Klebsiella pneumoniae is a common opportunistic pathogen causing nosocomial infections. One of the main virulence determinants of K. pneumoniae is the type 3 pilus (T3P). T3P helps the bacterial interaction to both abiotic and biotic surfaces and it is crucial for the biofilm formation. T3P is genetically organized in three transcriptional units: the mrkABCDF polycistronic operon, the mrkHI bicistronic operon and the mrkJ gene. MrkH is a regulatory protein encoded in the mrkHI operon, which positively regulates the mrkA pilin gene and its own expression. In contrast, the H-NS nucleoid protein represses the transcriptional expression of T3P. Here we reported that MrkH and H-NS positively and negatively regulate mrkJ expression, respectively, by binding to the promoter of mrkJ. MrkH protein recognized a sequence located at position -63.5 relative to the transcriptional start site of mrkJ gene. Interestingly, our results show that, in addition to its known function as classic transcriptional activator, MrkH also positively controls the expression of mrk genes by acting as an anti-repressor of H-NS; moreover, our results support the notion that high levels of MrkH repress T3P expression. Our data provide new insights about the complex regulatory role of the MrkH protein on the transcriptional control of T3P in K. pneumoniae.

Determination of Bacteriocin Genes and Antibacterial Activity of Lactobacillus Strains Isolated from Fecal of Healthy Individuals.

Lactobacillus species play a major role in gastrointestinal (GI) tract function, intestinal microbiota balance, and the immune system activity by exerting a strong activity against many intestinal pathogens. The aim of this study was to isolate Lactobacillus species from fecal samples, investigate their antimicrobial properties, and characterize their bacteriocin encoding genes. 48 fecal samples were grown in MRS broth and then MRS agar. The colonies grown in MRS agar were selected and identified by PCR. 72 Lactobacillus species were obtained from 434 lactic acid bacteria (LAB) strains. Approximately 40% of all Lactobacillus isolates had antimicrobial activity against one or more microorganisms and 17.4% of them were active against all four indicator bacteria. The frequency of bacteriocin encoding genes were 5 (6.9%), 3 (4.1%) and 5 (6.9%) for Gassericin A, Plantaricin S and Laf operon, respectively. pH alteration had no effect on antibacterial activity, but in the alkaline range these activities were reduced and the strains showed the highest antibacterial activity after 48 h incubation. These data indicate that the majority of isolates were susceptible to GI tract or belonged to other bacterial forms such as viable but nonculturable (VBNC). The detection of bacteriocin encoding genes in about only 6% of all Lactobacillus isolates seems to be due to the existence of many other bacteriocin encoding genes in Lactobacillus species which were not tested. Further study of the bacteriocin gene clusters, types, subtypes and the probiotic effect of these strains will contribute to a better characterization of these isolates.