Evolutionary relationship of the Bacillus licheniformis macrolide-lincosamide-streptogramin B resistance elements

Summary Naturally occurring erythromycin (Em) resistance was found in 11 of the 18 Bacillus licheniformis isolates tested but was absent from a wide variety of other Bacillus strains. The Em resistance elements confer inducible macrolide-lincosamide-streptogramin B (MLS) resistance and are related to ermD an MLS resistance element previously cloned from the chromosome of B. licheniformis 749. The MLS sensitive B. licheniformis strains and the other sensitive Bacillus strains tested, lack sequences with detectable homology to ermD. The sensitive B. licheniformis strains do exhibit homology to sequences which flank ermD in B. licheniformis 749. The relative sizes of the homologous DNA fragments suggest that the sensitive strains are lacking a 3.6 kb segment which contains ermD. It is shown that ermD is homologous to chromosomal DNA from Streptomyces erythreus ATCC 11635, an Em producing organism. These observations suggest to us that MLS resistance may have arisen in the Streptomyces and spread to B. licheniformis another gram positive bacterium found in soil. It is further proposed that ermD is or was located on a transposon-like element and has spread and evolved further to yeild a variety of related Staphylococcal and Streptococcal MLS determinants.     

Investigation of the Antimicrobial Activity of Bacillus licheniformis Strains Isolated from Retail Powdered Infant Milk Formulae

This study investigated the potential antimicrobial activity of ten Bacillus licheniformis strains isolated from retail infant milk formulae against a range of indicator (Lactococcus lactis, Lactobacillus bulgaricus and Listeria innocua) and clinically relevant (Listeria monocytogenes, Staphylococcus aureus, Streptococcus agalactiae, Salmonella Typhimurium and Escherichia coli) microorganisms. Deferred antagonism assays confirmed that all B. licheniformis isolates show antimicrobial activity against the Gram-positive target organisms. PCR and matrix-assisted laser desorption ionization time-of-flight mass spectrometry analyses indicated that four of the B. licheniformis isolates produce the bacteriocin lichenicidin. The remaining six isolates demonstrated a higher antimicrobial potency than lichenicidin-producing strains. Further analyses identified a peptide of ~1,422 Da as the most likely bioactive responsible for the antibacterial activity of these six isolates. N-terminal sequencing of the ~1,422 Da peptide from one strain identified it as ILPEITXIFHD. This peptide shows a high homology to the non-ribosomal peptides bacitracin and subpeptin, known to be produced by Bacillus spp. Subsequent PCR analyses demonstrated that the six B. licheniformis isolates may harbor the genetic machinery needed for the synthesis of a non-ribosomal peptide synthetase similar to those involved in production of subpeptin and bacitracin, which suggests that the ~1,422 Da peptide might be a variant of subpeptin and bacitracin.     

Novel whole-cell Reporter Assay for Stress-Based Classification of Antibacterial Compounds Produced by Locally Isolated Bacillus spp.

Reporter bacteria are beneficial for the rapid and sensitive screening of cultures producing peptide antibiotics, which can be an addition or alternative to the established antibiotics. This study was carried out to validate the usability of specific reporter strains for the target mediated identification of antibiotics produced by native Bacillus spp. isolated from different food sources. During preliminary classification, cell wall stress causing Bacillus isolates were screened by using reporter strain Bacillus subtilis BSF2470. The isolates which induced cell wall stress were further characterized for their specific mode of action by using other B. subtilis reporter strains (TMB 488, TMB 299 and TMB 279). The isolate B. licheniformis N12 was found to produce bacitracin confirmed by the response to reporter strain B. subtilis TMB 279 and by putative identification of bacitracin biosynthetic loci. The other isolate B. subtilis EC1 also induced B. subtilis TMB 279, but does not possess the bacitracin gene cluster indicating that it can be a novel, bacitracin like antibiotic. The different but related subsets of peptide antibiotics that bind the pyrophosphate moiety of the lipid carrier of cell wall biosynthesis can be identified using this whole cell based reporter strains.     

Characterization of Genes Encoding for Acquired Bacitracin Resistance in Clostridium perfringens

Phenotypic bacitracin resistance has been reported in Clostridium perfringens. However, the genes responsible for the resistance have not yet been characterized. Ninety-nine C. perfringens isolates recovered from broilers and turkeys were tested for phenotypic bacitracin resistance. Bacitracin MIC(90) (>256 μg/ml) was identical for both turkey and chicken isolates; whereas MIC(50) was higher in turkey isolates (6 μg/ml) than in chicken isolates (3 μg/ml). Twenty-four of the 99 isolates showed high-level bacitracin resistance (MIC breakpoint >256 μg/ml) and the genes encoding for this resistance were characterized in C. perfringens c1261_A strain using primer walking. Sequence analysis and percentages of amino acid identity revealed putative genes encoding for both an ABC transporter and an overproduced undecaprenol kinase in C. perfringens c1261_A strain. These two mechanisms were shown to be both encoded by the putative bcrABD operon under the control of a regulatory gene, bcrR. Efflux pump inhibitor thioridazine was shown to increase significantly the susceptibility of strain c1261_A to bacitracin. Upstream and downstream from the bcr cluster was an IS1216-like element, which may play a role in the dissemination of this resistance determinant. Pulsed-field gel electrophoresis with prior double digestion with I-CeuI/MluI enzymes followed by hybridization analyses revealed that the bacitracin resistance genes bcrABDR were located on the chromosome. Semi-quantitative RT-PCR demonstrated that this gene cluster is expressed under bacitracin stress. Microarray analysis revealed the presence of these genes in all bacitracin resistant strains. This study reports the discovery of genes encoding for a putative ABC transporter and an overproduced undecaprenol kinase associated with high-level bacitracin resistance in C. perfringens isolates from turkeys and broiler chickens.     

Production of Diarrheal Enterotoxins and Other Potential Virulence Factors by Veterinary Isolates of Bacillus Species Associated with Nongastrointestinal Infections

With the exceptions of Bacillus cereus and Bacillus anthracis, Bacillus species are generally perceived to be inconsequential. However, the relevance of other Bacillus species as food poisoning organisms and etiological agents in nongastrointestinal infections is being increasingly recognized. Eleven Bacillus species isolated from veterinary samples associated with severe nongastrointestinal infections were assessed for the presence and expression of diarrheagenic enterotoxins and other potential virulence factors. PCR studies revealed the presence of DNA sequences encoding hemolysin BL (HBL) enterotoxin complex and B. cereus enterotoxin T (BceT) in five B. cereus strains and in Bacillus coagulans NB11. Enterotoxin HBL was also harbored by Bacillus polymyxa NB6. After 18 h of growth in brain heart infusion broth, all seven Bacillus isolates carrying genes encoding enterotoxin HBL produced this toxin. Cell-free supernatant fluids from all 11 Bacillus isolates demonstrated cytotoxicity toward human HEp-2 cells; only one Bacillus licheniformis strain adhered to this test cell line, and none of the Bacillus isolates were invasive. This study constitutes the first demonstration that Bacillus spp. associated with serious nongastrointestinal infections in animals may harbor and express diarrheagenic enterotoxins traditionally linked to toxigenic B. cereus.     

A Novel EPS-Producing Strain of Bacillus licheniformis Isolated from a Shallow Vent Off Panarea Island (Italy)

A haloalkaliphilic, thermophilic Bacillus strain (T14), isolated from a shallow hydrothermal vent of Panarea Island (Italy), produced a new exopolysaccharide (EPS). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain T14 was highly related (99 % similarity) to Bacillus licheniformis DSM 13^T and Bacillus sonorensis DSM 13779^T. Further DNA–DNA hybridization analysis revealed 79.40 % similarity with B. licheniformis DSM 13^T and 39.12 % with B. sonorensis DSM 13779^T. Sucrose (5 %) was the most efficient carbon source for growth and EPS production. The highest EPS production (366 mg l^?1) was yielded in fermenter culture at 300 rpm after 48 h of incubation. The purified fraction EPS1 contained fructose/fucose/glucose/galactosamine/mannose in a relative proportion of 1.0:0.75:0.28:tr:tr and possessed a molecular weight of 1,000 kDa displaying a trisaccharide unit constituted by sugars with a β-manno-pyranosidic configuration. Screening for biological activity showed anti-cytotoxic effect of EPS1 against Avarol in brine shrimp test, indicating a potential use in the development of novel drugs.     

Distribution and variation of bacitracin synthetase gene sequences in laboratory stock strains of Bacillus licheniformis

Distribution and variation of bacitracin synthetase gene (bac) sequences in 22 laboratory stock strains of Bacillus licheniformis were studied by Southern hybridization of bac gene probes from B. licheniformis ATCC 10716 to genomic PstI or HindIII restriction fragments. Eleven strains gave hybridization signals. These hybridization patterns were classed into two types. Eight strains showed similar patterns to that of ATCC 10716 and all, except one, produced bacitracin. The three strains showed fairly different hybridization patterns from that of ATCC 10716, and one (ATCC 33632) of them produced bacitracin. None of the remaining 11 strains, including ATCC 14580 (type strain), gave any hybridization signals. All strains carrying bac gene sequences were erythromycin resistant. With one exception, all strains without bac gene sequences were erythromycin sensitive. These results show that B. licheniformis strains are divided into two groups with respect to presence of bac gene sequences and erythromycin resistance. Received: 5 September 2001 / Accepted: 19 October 2001     

In vitro assessment of probiotic properties of <Emphasis Type="Italic">Bacillus</Emphasis> isolated from naturally fermented congee from Inner Mongolia of China

A total of thirty-three strains of Bacillus were isolated from sixteen samples of naturally fermented congee in Inner Mongolia of China and identified by 16S rDNA sequence analysis. Probiotic properties including acid, bile tolerance and artificial gastrointestinal juice resistance as well as inhibition on pathogenic bacteria were used for screening of Bacillus. After the preliminary selection, four strains including Bacillus licheniformis IMAUB1002, Bacillus subtilis IMAUB1011, Bacillus amyloliquefaciens IMAUB1014 and Bacillus amyloliquefaciens IMAUB1034 showed high tolerance to simulated gastric juice at pH 2.0 for 3 h with survival rate all above 92%. And then through gastrointestinal transit, survival rates of these four strains were above 90%. Furthermore, Bacillus licheniformis IMAUB1002 performed well in tolerance to bile salt (0.6%) and inhibitory activity to five food-borne pathogens among four strains of Bacillus. The results suggested that Bacillus licheniformis IMAUB1002 should be considered as a potential probiotics. Further study will be focused on evaluation of these porbiotics properties in vivo and clarification of its other functional properties so as to use it in functional foods production in future.     

Diversity and enzymatic potentialities of <Emphasis Type="Italic">Bacillus</Emphasis> sp. strains isolated from a polluted freshwater ecosystem in Cuba

Genotypic and phenotypic characterization of Bacillus spp. from polluted freshwater has been poorly addressed. The objective of this research was to determine the diversity and enzymatic potentialities of Bacillus spp. strains isolated from the Almendares River. Bacilli strains from a polluted river were characterized by considering the production of extracellular enzymes using API ZYM. 14 strains were selected and identified using 16S rRNA, gyrB and aroE genes. Genotypic diversity of the Bacillus spp. strains was evaluated using pulsed field gel electrophoresis. Furthermore, the presence of genetic determinants of potential virulence toxins of the Bacillus cereus group and proteinaceous crystal inclusions of Bacillus thuringiensis was determined. 10 strains were identified as B. thuringiensis, two as Bacillus megaterium, one as Bacillus pumilus and one as Bacillus subtilis. Most strains produced proteases, amylases, phosphatases, esterases, aminopeptidases and glucanases, which reflect the abundance of biopolymeric matter in Almendares River. Comparison of the typing results revealed a spatio-temporal distribution among B. thuringiensis strains along the river. The results of the present study highlight the genotypic and phenotypic diversity of Bacillus spp. strains from a polluted river, which contributes to the knowledge of genetic diversity of Bacilli from tropical polluted freshwater ecosystems.     

Phylogeny in Aid of the Present and Novel Microbial Lineages: Diversity in Bacillus

Bacillus represents microbes of high economic, medical and biodefense importance. Bacillus strain identification based on 16S rRNA sequence analyses is invariably limited to species level. Secondly, certain discrepancies exist in the segregation of Bacillus subtilis strains. In the RDP/NCBI databases, out of a total of 2611 individual 16S rDNA sequences belonging to the 175 different species of the genus Bacillus, only 1586 have been identified up to species level. 16S rRNA sequences of Bacillus anthracis (153 strains), B. cereus (211 strains), B. thuringiensis (108 strains), B. subtilis (271 strains), B. licheniformis (131 strains), B. pumilus (83 strains), B. megaterium (47 strains), B. sphaericus (42 strains), B. clausii (39 strains) and B. halodurans (36 strains) were considered for generating species-specific framework and probes as tools for their rapid identification. Phylogenetic segregation of 1121, 16S rDNA sequences of 10 different Bacillus species in to 89 clusters enabled us to develop a phylogenetic frame work of 34 representative sequences. Using this phylogenetic framework, 305 out of 1025, 16S rDNA sequences presently classified as Bacillus sp. could be identified up to species level. This identification was supported by 20 to 30 nucleotides long signature sequences and in silico restriction enzyme analysis specific to the 10 Bacillus species. This integrated approach resulted in identifying around 30% of Bacillus sp. up to species level and revealed that B. subtilis strains can be segregated into two phylogenetically distinct groups, such that one of them may be renamed.     

Supplementations of ornithine and KNO3 enhanced bacitracin production by Bacillus licheniformis LC-11

During the fermentative process of Bacillus licheniformis LC-11, the dissolved oxygen (DO) and ornithine (Orn) content in the medium fell to zero, indicating that they were the potential limiting factors for cell growth and/or bacitracin biosynthesis. In addition, given that the nitrate-reducing system existing in B. licheniformis could favor cell anaerobiosis, the impacts of KNO₃ and Orn supplementations were therefore evaluated for improving bacitracin production in both a shaking flask and a 10-L fermentor. Orn supplementation (0.04 g/L) at 16 h or KNO₃ addition (0.5 g/L) in the production medium enhanced bacitracin production by 5.8 and 3.7 %, respectively. The combined effects of KNO₃ and Orn supplementations were then conducted via a two-level central composite design, resulting in a predicted maximum bacitracin yield of 821.81 U/mL if KNO₃ and Orn were supplemented at 514.39 mg/L and 45.35 mg/L, respectively. This predicated yield was then verified experimentally in a 10-L fermentor, achieving a 10.8 % increased bacitracin production (825 U/mL) over that of the control.     

Isolation, Characterization, and Identification of Bacterial Contaminants in Semifinal Gelatin Extracts

Bacterial contamination of gelatin is of great concern. Indeed, this animal colloid has many industrial applications, mainly in food and pharmaceutical products. In a previous study (E. De Clerck and P. De Vos, Syst. Appl. Microbiol. 25:611-618), contamination of a gelatin production process with a variety of gram-positive and gram-negative bacteria was demonstrated. In this study, bacterial contamination of semifinal gelatin extracts from several production plants was examined. Since these extracts are subjected to harsh conditions during production and a final ultrahigh-temperature treatment, the bacterial load at this stage is expected to be greatly reduced. In total, 1,129 isolates were obtained from a total of 73 gelatin batches originating from six different production plants. Each of these batches was suspected of having bacterial contamination based on quality control testing at the production plant from which it originated. For characterization and identification of the 1,129 bacterial isolates, repetitive-element PCR was used to obtain manageable groups. Representative strains were identified by means of 16S rRNA genesequencing, species-specific gyrB PCR, and gyrA and rpoB sequencing and were tested for gelatinase activity. The majority of isolates belonged to members of Bacillus or related endospore-forming genera. Representative strains were identified as Bacillus cereus, Bacillus coagulans, Bacillus fumarioli, Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus pumilus, Bacillus sonorensis, Bacillus subtilis, Bacillus gelatini, Bacillus thermoamylovorans, Anoxybacillus contaminans, Anoxybacillus flavithermus, Brevibacillus agri, Brevibacillus borstelensis, and Geobacillus stearothermophilus. The majority of these species include strains exhibiting gelatinase activity. Moreover, some of these species have known pathogenic properties. These findings are of great concern with regard to the safety and quality of gelatin and its applications.     

Distribution and characteristics of <Emphasis Type="Italic">Bacillus</Emphasis> bacteria associated with hydrobionts and the waters of the Peter the Great Bay,Sea of Japan

Bacilli of the species Bacillus subtilis, B. pumilus, B. mycoides, B. marinus and B. licheniformis (a total of 53 strains) were isolated from 15 invertebrate species and the water of the Vostok Bay, Peter the Great Bay, Sea of Japan. Bacilli were most often isolated from bivalves (22.7%) and sea cucumbers (18.9%); they occurred less frequently in sea urchins and starfish (13.2 and 7.5%, respectively). Most of bacilli strains were isolated from invertebrates inhabiting silted sediments. No Bacillus spp. strains were isolated from invertebrates inhabiting stony and sandy environments. The species diversity of bacilli isolated from marine objects under study was low. Almost all bacterial isolates were resistant to lincomycin. Unlike B. pumilus, B. subtilis isolates were mostly resistant to benzylpenicillin and ampicillin. Antibiotic sensitivity of B. licheniformis strains was variable (two strains were resistant to benzylpenicillin and oxacillin, while one was sensitive). A significant fraction of isolated bacilli contained pigments. Pigmented strains were more often isolated from seawater samples, while colorless ones predominated within hydrobionts. B. subtilis colonies had the broadest range of colors. In the Bacillus strains obtained, DNase, RNase, phosphatase, elastolytic, chitinase, and agarolytic activity was detected. Bacilli strains with hydrolytic activity occurred in invertebrates more often than in seawater.     

Interactions of Bacillus licheniformis ATCC 10716 and Normal Flora of Human Skin

To determine whether antibiotic production might be ecologically advantageous in the survival of Bacillus species on human skin, we applied spores of a bacitracin-producing strain of Bacillus licheniformis (ATCC 10716) to the forearms of 11 volunteers. Three additional strains of B. licheniformis which did not synthesize antibiotics, including a mutant of ATCC 10716, were used in subsequent control trials. Samples of flora were taken from inoculated and control (opposite forearm) sites during the colonization period, generally 3 weeks. Although population densities were unaltered, changes in the carriage, composition, and bacitracin sensitivity of resident flora were related with the presence of ATCC 10716 only, which suggests that microbial interactions are important in bacillus colonization and in maintenance of normal flora. Interactions were examined in vitro by comparing growth curves of representative skin bacteria, including isolates of Staphylococcus epidermidis, Staphylococcus saprophyticus, Micrococcus luteus, and a large-colony diphtheroid, grown individually, in mixed culture with each other, and together in presence of each test strain of B. licheniformis. We observed some diminution of growth of M. luteus and the diphtheroid in the first mixed culture, and the diphtheroid was completely retarded in common culture with ATCC 10716. Lesser antibiotic effects were seen on the cocci, whose rank of sensitivity was similar to that in vivo. The growth of the diphtheroid was enhanced in mixed culture with those strains of bacilli which lack antibiotic activity.     

Strains of <Emphasis Type="Italic">Bacillus</Emphasis> ssp. regulate wheat resistance to <Emphasis Type="Italic">Septoria nodorum</Emphasis> Berk.

The ability of Bacillus subtilis Cohn and Bacillus thuringiensis Berliner to induce systemic resistance in wheat plants to the casual agent of Septoria nodorum Berk., blotch has been studied. It has been shown that strains of Bacillus ssp. that possess the capacity for endophytic survival have antagonistic activity against this pathogen in vitro. A reduction of the degree of Septoria nodorum blotch development on wheat leaves under the influence of Bacillus spp. was accompanied by the suppression of catalase activity, an increase in peroxidase activity and H₂O₂ content, and expression of defence related genes such us PR-1, PR-6, and PR-9. It has been shown that B. subtilis 26 D induces expression levels of wheat pathogenesis-related (PR) genes which marks a SA-dependent pathway of sustainable development and that B. thuringiensis V-5689 and V-6066 induces a JA/ET-dependent pathway. These results suggest that these strain Bacillus spp. promotes the formation of wheat plant resistance to S. nodorum through systemic activation of the plant defense system. The designed bacterial consortium formed a complex biological response in wheat plants infected phytopathogen.     

Draft Genome Comparison of Representatives of the Three Dominant Genotype Groups of Dairy Bacillus licheniformis Strains

The spore-forming bacterium Bacillus licheniformis is a common contaminant of milk and milk products. Strains of this species isolated from dairy products can be differentiated into three major groups, namely, G, F1, and F2, using random amplification of polymorphic DNA (RAPD) analysis; however, little is known about the genomic differences between these groups and the identity of the fragments that make up their RAPD profiles. In this work we obtained high-quality draft genomes of representative strains from each of the three RAPD groups (designated strain G-1, strain F1-1, and strain F2-1) and compared them to each other and to B. licheniformis ATCC 14580 and Bacillus subtilis 168. Whole-genome comparison and multilocus sequence typing revealed that strain G-1 contains significant sequence variability and belongs to a lineage distinct from the group F strains. Strain G-1 was found to contain genes coding for a type I restriction modification system, urease production, and bacitracin synthesis, as well as the 8-kbp plasmid pFL7, and these genes were not present in strains F1-1 and F2-1. In agreement with this, all isolates of group G, but no group F isolates, were found to possess urease activity and antimicrobial activity against Micrococcus. Identification of RAPD band sequences revealed that differences in the RAPD profiles were due to differences in gene lengths, 3′ ends of predicted primer binding sites, or gene presence or absence. This work provides a greater understanding of the phylogenetic and phenotypic differences observed within the B. licheniformis species.     

Cellular fatty acid profile and H+-ATPase activity to assess acid tolerance of Bacillus sp. for potential probiotic functional attributes

The present study has been focused widely on comparative account of probiotic qualities of Bacillus spp. for safer usage. Initially, 170 heat resistant flora were isolated and selected for non-pathogenic cultures devoid of cytK, hblD, and nhe1 virulence genes. Subsequently, through biochemical tests along with 16S rRNA gene sequencing and fatty acid profiling, the cultures were identified as Bacillus megaterium (AR-S4), Bacillus subtilis (HR-S1), Bacillus licheniformis (Csm1-1a and HN-S1), and Bacillus flexus (CDM4-3c and CDM3-1). The selected cultures showed 70–80 % survival under simulated gastrointestinal condition which was also confirmed through H⁺-ATPase production. The amount of H⁺-ATPase increased by more than 2-fold when grown at pH 2 which support for the acid tolerance ability of Bacillus isolates. The study also examined the influence of acidic pH on cellular fatty acid composition of Bacillus spp. A remarkable shift in the fatty acid profile was observed at acidic pH through an increased amount of even numbered fatty acid (C16 and C18) in comparison with odd numbered (C15 and C17). Additionally, the cultures exhibited various probiotic functional properties. Overall, the study increases our understanding of Bacillus spp. and will allow both industries and consumers to choose for well-defined probiotic with possible health benefits.     

A look into a multifunctional toolbox: endophytic <Emphasis Type="Italic">Bacillus</Emphasis> species provide broad and underexploited benefits for plants

One of the major challenges of agriculture currently is to obtain higher crop yield. Environmental conditions, cultivar quality, and plant diseases greatly affect plant productivity. On the other hand, several endophytic Bacillus species have emerged as a complementary, efficient, and safe alternative to current crop management practices. The ability of Bacillus species to form spores, which resist adverse conditions, is an advantage of the genus for use in formulations. Endophytic Bacillus species provide plants with a wide range of benefits, including protection against phytopathogenic microorganisms, insects, and nematodes, eliciting resistance, and promoting plant growth, without causing damage to the environment. Bacillus thuringiensis, B. subtilis, B. amyloliquefaciens, B. velezensis, B. cereus, B. pumilus, and B. licheniformis are the most studied Bacillus species for application in agriculture, although other species within the genus have also shown great potential. Due to the increasing number of whole-genome sequenced endophytic Bacillus spp. strains, various bioactive compounds have been predicted. These data reveal endophytic Bacillus species as an underexploited source of novel molecules of biotechnological interest. In this review, we discuss how endophytic Bacillus species are a valuable multifunctional toolbox to be integrated with crop management practices for achieving higher crop yield.     

Investigation of antibacterial activity of Bacillus spp. isolated from the feces of Giant Panda and characterization of their antimicrobial gene distributions

Bacillus group is a prevalent community of Giant Panda’s intestinal flora, and plays a significant role in the field of biological control of pathogens. To understand the diversity of Bacillus group from the Giant Panda intestine and their functions in maintaining the balance of the intestinal microflora of Giant Panda, this study isolated a significant number of strains of Bacillus spp. from the feces of Giant Panda, compared the inhibitory effects of these strains on three common enteric pathogens, investigated the distributions of six universal antimicrobial genes (ituA, hag, tasA, sfp, spaS and mrsA) found within the Bacillus group by PCR, and analyzed the characterization of antimicrobial gene distributions in these strains using statistical methods. The results suggest that 34 strains of Bacillus spp. were isolated which has not previously been detected at such a scale, these Bacillus strains could be classified into five categories as well as an external strain by 16S rRNA; Most of Bacillus strains are able to inhibit enteric pathogens, and the antimicrobial abilities may be correlated to their categories of 16S rRNA; The detection rates of six common antimicrobial genes are between 20.58 %(7/34) and 79.41 %(27/34), and genes distribute in three clusters in these strains. We found that the antimicrobial abilities of Bacillus strains can be one of the mechanisms by which Giant Panda maintains its intestinal microflora balance, and may be correlated to their phylogeny.     

Naturally occurring antibiotic resistance inBacillus sphaericus andBacillus licheniformis

Bacillus sphaericus is an aerobic, spore-forming, gram-variable bacillus. Certain strains of this organism are extremely pathogenic for mosquito larvae. Strains from four different serotypes ofB. sphaericus were found to be naturally resistant to streptomycin and to chloramphenicol. Both entomocidal and nonentomocidal strains of this organism exhibited similar patterns of resistance to these antimicrobial agents. In contrast, other members of the genusBacillus, includingB. subtilis, B. thuringiensis, B. laterosporus, andB. amyloliquefaciens, proved to be quite sensitive to these antibiotics. Four strains ofB. licheniformis were found to be resistant to chloramphenicol but sensitive to streptomycin.