Isolation, identification and characterization of fluoride resistant bacteria: Possible role in bioremediation

Microorganisms found in industrial effluents and near the sites of the contamination can be used to indicate pollution and detoxify the contaminated water resources. Emergence of xenobiotic resistant bacteria among them might be potential application in bioremediation. The objective of this study was to isolate and characterize fluoride resistant bacteria from soil and water samples of different regions of India. Five isolates were recovered from different samples which were found to be fluoride resistant. Two of them effectively reduced the fluoride from their media. Through the current study it can be predicted that fluoride pollution results in selective pressure that leads to the development of fluoride resistant among bacterial populations, probably through the mechanism which involved high affinity anion binding compounds called ionophores. Resistant microbes may play a bioremediative role by transforming and concentrating these anions so that they are less available and less dangerous.     

Isolation, identification and characterization of fluoride resistant bacteria: possible role in bioremediation

Microorganisms found in industrial effluents and near the sites of the contamination can be used to indicate pollution and detoxify the contaminated water resources. Emergence of xenobiotic resistant bacteria among them might be potential application in bioremediation. The objective of this study was to isolate and characterize fluoride resistant bacteria from soil and water samples of different regions of India. Five isolates were recovered from different samples which were found to be fluoride resistant. Two of them effectively reduced the fluoride from their media. Through the current study it can be predicted that fluoride pollution results in selective pressure that leads to the development of fluoride resistant among bacterial populations, probably through the mechanism which involved high affinity anion binding compounds called ionophores. Resistant microbes may play a bioremediative role by transforming and concentrating these anions so that they are less available and less dangerous.     

Glucuronidation of 3'-azido-3'-deoxythymidine in human liver microsomes: enzyme inhibition by drugs and steroid hormones.

The molecular form of UDP-glucuronosyltransferase involved in the catalysis of 3'-azido-3'-deoxythymidine (AZT)-5'-O-glucuronide was characterized in human liver microsomes. The specific activity (1.3 nmol/min per mg protein) in transplantable liver was more than 2-times higher than in post-mortem fragments. Liver microsomes from patients suffering Crigler-Najjar syndrome, who are genetically deficient in bilirubin UDP-glucuronosyltransferase, could also glucuronidate AZT to a similar extent, thus indicating that this protein was not involved in that process. A genetically engineered V79 cell line stably expressing a cDNA which encodes a human isozyme active towards 1-naphthol was unable to glucuronidate AZT. Clinically used drugs, most of them being glucuronidated, were tested as potential inhibitors of the glucuronidation of AZT in human liver microsomes. The drugs chemically related to 2-phenylpropionic acid, naproxen and flurbiprofen, and the steroid compounds testosterone, estrone and ethynylestradiol strongly inhibited AZT glucuronidation. Codeine and morphine also decreased the reaction rate although to a lower extent. Except estrone which elicited a partial competitive inhibition, ethynylestradiol, flurbiprofen naproxen and testosterone could competitively inhibit AZT glucuronidation with an apparent Ki of 38, 50, 172 and 250 microM, respectively. The results suggest that these drugs were substrates of the same isozyme(s) involved in AZT glucuronidation. Probenecid was a weak inhibitor of the reaction (Ki 900 microM), only when non-disrupted microsomes were used. This drug may compete with the anion carrier system involved in the microsomal uptake of UDP-glucuronic acid.     

Microsatellite analysis reveals marked genetic differentiation between Haemonchus contortus laboratory isolates and provides a rapid system of genetic fingerprinting

Many of the Haemonchus contortus isolates currently used for experimental work were originally derived from different regions of the world and are commonly exchanged between laboratories. In most cases, these are largely genetically uncharacterised other than the analyses conducted on specific genes of interest. We have used a panel of eight microsatellite markers to genetically characterise five different commonly used H. contortus isolates including MHco3 (ISE), the isolate chosen for full genome sequencing as part of the H. contortus genome project. There is an extremely high level of genetic differentiation between each of the isolates except the two which have a common origin, MHco1 (MOSI) and MHco3 (ISE). We have investigated the amplification of microsatellite markers from pooled DNA as a potential method for fingerprinting different isolates. Good estimates of the true allele frequencies can be made by amplification from either pooled adult DNA or bulk L3 DNA for seven out of the eight markers tested. Both single worm genotyping and bulk DNA fingerprinting revealed no genetic differentiation between adult worms in the host and larvae derived from faecal culture. Furthermore, none of the eight markers showed genetic changes when isolates were passaged through different individual hosts. Hence the microsatellite genotyping of bulk larval DNA samples provides a simple and rapid method to genetically define and monitor laboratory isolates, and to determine their relationship with particular field populations.     

A sensitive nonisotopic method for the determination of intracellular azidothymidine 5'-mono-, 5'-di-, and 5'-triphosphate.

In order to analyze the efficacy of azidothymidine (AZT), it is important to know intracellular concentrations of AZT metabolites. However, it has been impossible to measure intracellular AZT 5'-monophosphate (AZT-MP), AZT 5'-diphosphate (AZT-DP), and AZT 5'-triphosphate (AZT-TP) without using isotopes. In the present study, we developed a new method to measure intracellular AZT metabolites without radiolabeled compounds. The method employed was a high-performance liquid chromatography (HPLC) system programmed for column switching technique, in which two columns were used: column 1 (TSK-G2000-SW, 300 x 7.5 mm) to preseparate AZT metabolites from major cell components, and column 2 (YMC-A-312-ODS, 150 x 6 mm) to determine the metabolites. The limit of detectability of this system was 3.3 pmol/injection. When MT-4 cells were incubated with various concentrations of AZT, intracellular concentrations of AZT-MP increased in parallel with extracellular AZT. Those of AZT-DP and AZT-TP, however, reached plateaus at 5 and 2 microM of AZT, respectively. In MT-4 and Molt-4 cells incubated with 5 microM AZT, concentrations of AZT-MP increased time dependently, while the AZT-DP/AZT-MP ratios decreased with time. These data suggest that high dose of AZT may not necessarily increase intracellular concentration of AZT-TP. The concentrations of AZT metabolites in peripheral blood mononuclear cells in a patient with AIDS and an asymptomatic carrier were measured; the concentrations were comparable to those in cultured cells. Quantitative analysis of intracellular AZT metabolites without the use of isotopes will increase safety and convenience of measurement, and take an effective step in studying pharmacokinetics of AZT in clinical materials.     

瘤胃中木质纤维素降解菌及降解酶基因的研究进展

摘要：反刍动物瘤胃是公认的木质纤维素高效降解的天然反应器,对瘤胃微生物的研究成为开发生物能源的热点领域之一。其研究手段已经从传统的依赖分离培养从瘤胃中获得木质纤维素降解菌,并对降解菌中的木质纤维素降解酶逐一分析,发展到通过基因组/元基因组技术,直接从瘤胃中发现获得大量新的木质纤维素降解酶基因/基因簇,进而探讨其降解的分子机理。已有的研究结果表明,瘤胃微生物降解木质纤维素的过程非常复杂,其中涉及到大量不同种类的微生物、酶及基因/基因簇,随着新分析技术的建立和完善,对这些微生物、酶和基因的研究已取得了诸多进展。本论文综述报道了近期有关该方向的研究进展。     

Genetic comparison of Bacillus anthracis and its close relatives using amplified fragment length polymorphism and polymerase chain reaction analysis

Amplified fragment length polymorphism (AFLP) analysis allows a rapid, relatively simple analysis of a large portion of a microbial genome, providing information about the species and its phylogenetic relationship to other microbes (Vos et al. 1995). The method simply surveys the genome for length and sequence polymorphisms. The AFLP pattern identified can be used for comparison to the genomes of other species. Unlike other methods, it does not rely on analysis of a single genetic locus that may bias the interpretation of results and does not require any prior knowledge of the targeted organism. Moreover, a standard set of reagents can be applied to any species without using species-specific information or molecular probes. We are using AFLP analysis to rapidly identify different bacterial species. A comparison of AFLP profiles generated from a large battery of Bacillus anthracis strains shows very little variability among different isolates (Keim et al. 1997). By contrast, there is a significant difference between AFLP profiles generated for any B. anthracis strain and even the most closely related Bacillus species. Sufficient variability is apparent among all known microbial species to allow phylogenetic analysis based on large numbers of genetically unlinked loci. These striking differences among AFLP profiles allow unambiguous identification of previously identified species and phylogenetic placement of newly characterized isolates relative to known species based on a large number of independent genetic loci. Data generated thus far show that the method provides phylogenetic analyses that are consistent with other widely accepted phylogenetic methods. However, AFLP analysis provides a more detailed analysis of the targets and samples a much larger portion of the genome. Consequently, it provides an inexpensive, rapid means of characterizing microbial isolates to further differentiate among strains and closely related microbial species. Such information cannot be rapidly generated by other means. AFLP sample analysis quickly generates a very large amount of molecular information about microbial genomes. However, this information cannot be analysed rapidly using manual methods. We are developing a large archive of electronic AFLP signatures that is being used to identify isolates collected from medical, veterinary, forensic and environmental samples. We are also developing the computational packages necessary to rapidly and unambiguously analyse the AFLP profiles and conduct a phylogenetic comparison of these data relative to information already in our database. We will use this archive and the associated algorithms to determine the species identity of previously uncharacterized isolates and place them phylogenetically relative to other microbes based on their AFLP signatures. This study provides significant new information about microbes with environmental, veterinary and medical significance. This information can be used in further studies to understand the relationships among these species and the factors that distinguish them from one another. It should also allow the identification of unique factors that contribute to important microbial traits, including pathogenicity and virulence. We are also using AFLP data to identify, isolate and sequence DNA fragments that are unique to particular microbial species and strains. The fragment patterns and sequence information provide insights into the complexity and organization of bacterial genomes relative to one another. They also provide the information necessary for the development of species-specific polymerase chain reaction primers that can be used to interrogate complex samples for the presence of B. anthracis, other microbial pathogens or their remnants.     

Microbial hitchhikers on intercontinental dust: high-throughput sequencing to catalogue microbes in small sand samples

Microbiological studies on the intercontinental transport of dust are confounded by the difficulty of obtaining sufficient material for analysis. Axenic samples of dust collected at high altitudes or historic specimens in museums are often so small and precious that the material can only be sacrificed when positive results are assured. With this in mind, we evaluated current methods and developed new ones in an attempt to catalogue all microbes present in small dust or sand samples. The methods used included classical microbiological approaches in which sand extracts were plated out on a variety of different media, polymerase chain reaction (PCR)-based amplification of 16S/18S rRNA sequences followed by construction of clone libraries, PCR amplification of 16S rRNA sequences followed by high-throughput sequencing (HtS) of the products and direct HtS of DNA extracted from the sand. A representative sand sample collected at Bahaï Wadi in the desert of the Republic of Chad was used. HtS with or without amplification showed the most promise and can be performed on ≤100 ng DNA. Since living microbes are often required, current best practices would involve geochemical and microscopic characterisation of the sample, followed by DNA isolation and direct HtS. Once the microbial content of the sample has been deciphered, growth conditions (including media) can be tailored to isolate the micro-organisms of interest.     

Detection and genetic characterization of enteroviruses circulating among wild populations of chimpanzees in Cameroon: relationship with human and simian enteroviruses

Enteroviruses (EVs), members of the family Picornaviridae, are a genetically and antigenically diverse range of viruses causing acute infections in humans and several Old World monkey (OWM) species. Despite their known wide distribution in primates, nothing is currently known about the occurrence, frequency, and genetic diversity of enteroviruses infecting apes. To investigate this, 27 chimpanzee and 27 gorilla fecal samples collected from undisturbed jungle areas with minimal human contact in Cameroon were screened for EVs. Four chimpanzee samples were positive, but none of the gorilla samples were positive. Genetic characterization of the VP1, VP4, and partial VP2 genes, the 5' untranslated region, and partial 3Dpol sequences enabled chimpanzee-derived EVs to be identified as (i) the species A type, EV76, (ii) a new species D type assigned as EV111, along with a human isolate from the Democratic Republic of Congo previously described by the International Committee on the Taxonomy of Viruses, and (iii) a new species B type (assigned as EV110) most closely related to, although a distinct type from, the SA5 isolate recovered from a vervet monkey. The identification of EVs infecting chimpanzees related to those circulating in human and OWM populations provides evidence for cross-species transmission of EVs between primates. However, the direction of transfer and the existence of primate sources of zoonotic enterovirus infections in humans require further investigation of population exposure and more extensive characterization of EVs circulating in wild ape populations.     

Development cycles of coryneform and Nocardia-like bacteria

The growth cycles and the types of cell separation were studied in a microchamber with the collection strains of Brevibacterium ammoniagenes ATTC 6871, B. helvolum ATCC 19239, B. linens CCM 47 and ATCC 9174, B. maris VKM B-464 and B. stationis ATCC 14403, as well as with the strains of the genus Rhodococcus isolated from soils, viz. R. maris sp. nov. IMB 283 and R. luteus sp. nov. IMB 385. According to the increasing complexity of cellular morphological transformation in the life cycle, the organisms may be arranged in a series: R. maris -- B. ammoniagenes -- B. stationis -- B. linens -- B. helvolum -- R. luteus. The first three organisms are characterized by the snapping type of separation of short rod-like daughter cells. The cells of B. linens separate by both the snapping and bending types. The coccoid cells of B. helvolum ATCC 19239 produce many buds which are transformed into rod-like cells in the course of growth. In the log phase of growth, both true and false branching of the cells is observed; the latter is the result of a peculiar growth of the ends in the separated cells of B. helvolum. The cells of R. luteus form a rudimentary, rapidly fragmenting mycelium whose rod-like elements divide then by binary fission; the daughter cells separate the bending and snapping types.     

具细菌群体感应抑制活性海洋细菌的筛选鉴定

目的:从海洋环境中筛选对细菌群体感应有抑制作用的活性菌株,为以致病菌群体感应系统为靶点的新型疗法提供新的药用资源。方法:从海水中分离纯化细菌菌株,采用根癌农杆菌平板筛选模型筛选细菌群体感应抑制活性细菌,对筛选出的海洋细菌进行生理生化和16S rDNA序列测定,根据《伯杰氏手册》进行菌种分类鉴定。结果:从217株海洋细菌中筛选出1株能显著抑制细菌群体感应效应的海洋细菌Y2,该海洋细菌具有蜡样芽孢杆菌(Bacillus cereus)的典型特征,其16S rDNA序列与GenBank中蜡样芽孢杆菌16S rDNA的部分序列有100%的同源性。结论:海洋环境中也存在具有抑制细菌群体感应活性的微生物。     

Penicillium strains as dominant degraders in soil for coffee residue, a biological waste unsuitable for fertilization

AIMS: Coffee residue is an agricultural waste which inhibits the growth of several crops. Therefore coffee residue-degrading microbes in soil were screened, isolated and characterized. METHODS AND RESULTS: Forty isolates were obtained after enrichment culture of soil samples. Seven strains (fast degraders) showed strong degrading activity, while 18 strains (slow degraders) showed weak degrading activity. DNA analysis suggested that the fast degraders are Penicillium, and the slow degraders are Penicillium, Trichoderma/Hypocrea, Fusarium/Gibberella, Phaeoacremonium/Togninia or Acidocella. The all fast degraders are cellulolytic, mannolytic and pectinolytic. CONCLUSIONS: Although it is generally thought that fungi such as Trichoderma contribute largely to aerobic degradation of cellulosic biomass, our data suggested that Penicillium overwhelms them in coffee residue degradation. It was implied that polysaccharides in coffee residue are not degraded independently by different microbes, but degraded simultaneously by strains with cellulolytic, mannolytic and pectinolytic activity. Since there is no report of an ascomycete possessing all the three enzyme activities, the fast degraders are ecologically important and have the potential to be used as producers of the costly enzymes from agricultural wastes. SIGNIFICANCE AND IMPACT OF STUDY: The present results advance our understanding of microbial degradation of a phytotoxic agricultural waste, and offer a new tool for recycling it.     

Directed evolution of thymidine kinase for AZT phosphorylation using DNA family shuffling

The thymidine kinase (TK) genes from herpes simplex virus (HSV) types 1 and 2 were recombined in vitro with a technique called DNA family shuffling. A high-throughput robotic screen identified chimeras with an enhanced ability to phosphorylate zidovudine (AZT). Improved clones were combined, reshuffled, and screened on increasingly lower concentrations of AZT. After four rounds of shuffling and screening, two clones were isolated that sensitize Escherichia coli to 32-fold less AZT compared with HSV-1 TK and 16,000-fold less than HSV-2 TK. Both clones are hybrids derived from several crossover events between the two parental genes and carry several additional amino acid substitutions not found in either parent, including active site mutations. Kinetic measurements show that the chimeric enzymes had acquired reduced K(M) for AZT as well as decreased specificity for thymidine. In agreement with the kinetic data, molecular modeling suggests that the active sites of both evolved enzymes better accommodate the azido group of AZT at the expense of thymidine. Despite the overall similarity of the two chimeric enzymes, each contains key contributions from different parents in positions influencing substrate affinity. Such mutants could be useful for anti-HIV gene therapy, and similar directed-evolution approaches could improve other enzyme-prodrug combinations.     

Comparison of Enterococcus faecium and Enterococcus faecalis Strains Isolated from Water and Clinical Samples: Antimicrobial Susceptibility and Genetic Relationships

Enterococci are part of the normal intestinal flora in a large number of mammals, and these microbes are currently used as indicators of fecal contamination in water and food for human consumption. These organisms are considered one of the primary causes of nosocomial and environmental infections due to their ability to survive in the environment and to their intrinsic resistance to antimicrobials. The aims of this study were to determine the biochemical patterns and antimicrobial susceptibilities of Enterococcus faecalis and E. faecium isolates from clinical samples and from water (groundwater, water from the Xochimilco wetland, and treated water from the Mexico City Metropolitan Area) and to determine the genetic relationships among these isolates. A total of 121 enterococcus strains were studied; 31 and 90 strains were isolated from clinical samples and water (groundwater, water from the Xochimilco wetland, and water for agricultural irrigation), respectively. Identification to the species level was performed using a multiplex PCR assay, and antimicrobial profiles were obtained using a commercial kit. Twenty-eight strains were analyzed by pulsed-field gel electrophoresis (PFGE). E. faecium strains isolated from water showed an atypical biochemical pattern. The clinical isolates showed higher resistance to antibiotics than those from water. Both the enterococci isolated from humans, and those isolated from water showed high genetic diversity according to the PFGE analysis, although some strains seemed to be closely related. In conclusion, enterococci isolated from humans and water are genetically different. However, water represents a potential route of transmission to the community and a source of antimicrobial resistance genes that may be readily transmitted to other, different bacterial species.     

一株花生根际铁载体产生菌的分离鉴定及耐药性分析

目的：从花生根际筛选铁载体产生能力较强的菌株,对其进行鉴定及耐药性分析。方法：用梯度稀释法从花生根际中分离出细菌,在刃天青（CAS）检测平板上依显色圈的大小从中筛选出一株铁载体产生能力较强的菌,并对其进行生理生化鉴定和16S rDNA序列分析,用抗生素梯度平板检测其对9种常见抗生素的抗性。结果：筛选出一株产铁载体的菌株D15,13项生理生化指标除甲基红试验呈阳性外,其他均与恶臭假单胞菌相同;其16S rDNA与恶臭假单胞菌的同源性为100%;该菌对氨苄青霉素、氯霉素、利福平、红霉素、新霉素、链霉素、四环素都有不同程度的的抗性,对卡那霉素和庆大霉素表现较强的敏感性。结论：获得铁载体产生菌D15,经鉴定为恶臭假单胞菌,该菌耐药性符合用转座子诱变法研究铁载体合成的相关基因的条件。     

Isolation, characterization and mapping of genes differentially expressed during fibre development between Gossypium hirsutum and G. barbadense by cDNA-SRAP

Gossypium hirsutum and G. barbadense are two cultivated tetraploid cotton species with differences in fibre quality. The fibre of G. barbadense is longer, stronger and finer than that of G. hirsutum. To isolate genes expressed differently between the two species during fibre development, cDNA-SRAP (sequence-related amplified polymorphism) was applied. This technique was used to analyse genes at different stages of fibre development in G. hirsutum cv. Emian22 and G. barbadense acc. 3-79, the parents of our interspecific mapping population. A total of 4096 SRAP primer combinations were used to screen polymorphism between the DNA of the parents, and 275 highly polymorphic primers were picked out to analyse DNA and RNA from leaves and fibres at different developmental stages of the parents. A total of 168 DNA fragments were isolated from gels and sequenced: 54, 30, 38 and 41 from fibres of 5, 10, 15 and 20 days post-anthesis, respectively, and five from multi stages. To genetically map these sequences, 104 sequence-specific primers were developed and were used to screened polymorphism between the mapping parents. Finally, six markers were mapped on six chromosomes of our backbone interspecific genetic map. This work can give us a primary knowledge of differences in mechanism of fibre development between G. hirsutum and G. barbadense.     

Locally isolated yeasts from Malaysia: identification, phylogenetic study and characterization

Yeasts are a convenient platform for many applications. They have been widely used as the expression hosts. There is a need to have a new yeast expression system to contribute the molecular cloning demands. Eight yeast isolates were screened from various environment sources and identified through ribosomal DNA (rDNA) Internal Transcribed Spacer (ITS). Full sequence of the rDNA ITS region for each isolate was BLASTed and phylogenetic study was constructed by using MEGA4. Among the isolates, isolate WB from 'ragi' (used to ferment carbohydrates) could be identified as a new species in order Saccharomycetales according to rDNA ITS region, morphology and biochemical tests. Isolate SO (from spoiled orange), RT (rotten tomato) and RG (different type of 'ragi') were identified as Pichia sp. Isolates R1 and R2, S4 and S5 (from the surrounding of a guava tree) were identified as Issatchenkia sp. and Hanseniaspora sp., respectively. Geneticin, 50 μg/mL, was determined to be the antibiotic marker for all isolates excepted for isolates RT and SO which used 500 μg/mL and 100 μg/mL Zeocin, respectively. Intra-extracellular proteins were screened for lipolytic activity at 30°C and 70°C. Thermostable lipase activity was detected in isolates RT and R1 with 0.6 U/mg and 0.1 U/mg, respectively. In conclusion, a new yeast-vector system for isolate WB can be developed by using phleomycin or geneticin as the drugs resistance marker. Moreover, strains RT and R1 can be investigated as a novel source of a thermostable lipase.     

Screening of Marine Bacterial Producers of Polyunsaturated Fatty Acids and Optimisation of Production

Water samples from three different environments including Mid Atlantic Ridge, Red Sea and Mediterranean Sea were screened in order to isolate new polyunsaturated fatty acids (PUFAs) bacterial producers especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Two hundred and fifty-one isolates were screened for PUFA production and among them the highest number of producers was isolated from the Mid-Atlantic Ridge followed by the Red Sea while no producers were found in the Mediterranean Sea samples. The screening strategy included a simple colourimetric method followed by a confirmation via GC/MS. Among the tested producers, an isolate named 66 was found to be a potentially high PUFA producer producing relatively high levels of EPA in particular. A Plackett–Burman statistical design of experiments was applied to screen a wide number of media components identifying glycerol and whey as components of a production medium. The potential low-cost production medium was optimised by applying a response surface methodology to obtain the highest productivity converting industrial by-products into value-added products. The maximum achieved productivity of EPA was 20 mg/g, 45 mg/l, representing 11 % of the total fatty acids, which is approximately five times more than the amount produced prior to optimisation. The production medium composition was 10.79 g/l whey and 6.87 g/l glycerol. To our knowledge, this is the first investigation of potential bacteria PUFA producers from Mediterranean and Red Seas providing an evaluation of a colourimetric screening method as means of rapid screening of a large number of isolates.     

Conservation and diversity of seed associated endophytes in Zea across boundaries of evolution, ethnography and ecology

Endophytes are non-pathogenic microbes living inside plants. We asked whether endophytic species were conserved in the agriculturally important plant genus Zea as it became domesticated from its wild ancestors (teosinte) to modern maize (corn) and moved from Mexico to Canada. Kernels from populations of four different teosintes and 10 different maize varieties were screened for endophytic bacteria by culturing, cloning and DNA fingerprinting using terminal restriction fragment length polymorphism (TRFLP) of 16S rDNA. Principle component analysis of TRFLP data showed that seed endophyte community composition varied in relation to plant host phylogeny. However, there was a core microbiota of endophytes that was conserved in Zea seeds across boundaries of evolution, ethnography and ecology. The majority of seed endophytes in the wild ancestor persist today in domesticated maize, though ancient selection against the hard fruitcase surrounding seeds may have altered the abundance of endophytes. Four TRFLP signals including two predicted to represent Clostridium and Paenibacillus species were conserved across all Zea genotypes, while culturing showed that Enterobacter, Methylobacteria, Pantoea and Pseudomonas species were widespread, with γ-proteobacteria being the prevalent class. Twenty-six different genera were cultured, and these were evaluated for their ability to stimulate plant growth, grow on nitrogen-free media, solubilize phosphate, sequester iron, secrete RNAse, antagonize pathogens, catabolize the precursor of ethylene, produce auxin and acetoin/butanediol. Of these traits, phosphate solubilization and production of acetoin/butanediol were the most commonly observed. An isolate from the giant Mexican landrace Mixteco, with 100% identity to Burkholderia phytofirmans, significantly promoted shoot potato biomass. GFP tagging and maize stem injection confirmed that several seed endophytes could spread systemically through the plant. One seed isolate, Enterobacter asburiae, was able to exit the root and colonize the rhizosphere. Conservation and diversity in Zea-microbe relationships are discussed in the context of ecology, crop domestication, selection and migration.