Biomedical subjects

Kasthuri Venkateswaran

Publications and source records attributed to Kasthuri Venkateswaran.

At least 19 recordsLinked to original sources

PubMed2024

Neobacillus driksii sp. nov. isolated from a Mars 2020 spacecraft assembly facility and genomic potential for lasso peptide production in Neobacillus.

UNLABELLED: During microbial surveillance of the Mars 2020 spacecraft assembly facility, two novel bacterial strains, potentially capable of producing lasso peptides, were identified. Characterization using a polyphasic taxonomic approach, whole-genome sequencing and phylogenomic analyses revealed a close genetic relationship among two strains from Mars 2020 cleanroom floors (179-C4-2-HS, 179-J1A1-HS), one strain from the Agave plant (AT2.8), and another strain from wheat-associated soil (V4I25). All four strains exhibited high 16S rRNA gene sequence similarity (>99.2%) and low average nucleotide identity (ANI) with Neobacillus niacini NBRC 15566T, delineating new phylogenetic branches within the genus. Detailed molecular analyses, including gyrB (90.2%), ANI (86.4%), average amino acid identity (87.8%) phylogenies, digital DNA-DNA hybridization (32.6%), and percentage of conserved proteins (77.7%) indicated significant divergence from N. niacini NBRC 15566T. Consequently, these strains have been designated Neobacillus driksii sp. nov., with the type strain 179-C4-2-HST (DSM 115941T = NRRL B-65665T). N. driksii grew at 4°C to 45°C, pH range of 6.0 to 9.5, and 0.5% to 5% NaCl. The major cellular fatty acids are iso-C15:0 and anteiso-C15:0. The dominant polar lipids include diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and an unidentified aminolipid. Metagenomic analysis within NASA cleanrooms revealed that N. driksii is scarce (17 out of 236 samples). Genes encoding the biosynthesis pathway for lasso peptides were identified in all N. driksii strains and are not commonly found in other Neobacillus species, except in 7 out of 26 recognized species. This study highlights the unique metabolic capabilities of N. driksii, underscoring their potential in antimicrobial research and biotechnology. IMPORTANCE: The microbial surveillance of the Mars 2020 assembly cleanroom led to the isolation of novel N. driksii with potential applications in cleanroom environments, such as hospitals, pharmaceuticals, semiconductors, and aeronautical industries. N. driksii genomes were found to possess genes responsible for producing lasso peptides, which are crucial for antimicrobial defense, communication, and enzyme inhibition. Isolation of N. driksii from cleanrooms, Agave plants, and dryland wheat soils, suggested niche-specific ecology and resilience under various environmentally challenging conditions. The discovery of potent antimicrobial agents from novel N. driksii underscores the importance of genome mining and the isolation of rare microorganisms. Bioactive gene clusters potentially producing nicotianamine-like siderophores were found in N. driksii genomes. These siderophores can be used for bioremediation to remove heavy metals from contaminated environments, promote plant growth by aiding iron uptake in agriculture, and treat iron overload conditions in medical applications.

Phylogeny↗

PubMed2006

Shewanella hafniensis sp. nov. and Shewanella morhuae sp. nov., isolated from marine fish of the Baltic Sea.

Two novel species belonging to the genus Shewanella are described on the basis of their phenotypic characteristics, phylogenetic analyses of 16S rRNA and gyrB gene sequences and levels of DNA-DNA hybridization. A total of 47 strains belonging to two novel Gram-negative, psychrotolerant, H2S-producing bacterial species were isolated from marine fish (cod and flounder) caught from the Baltic Sea off Denmark. The phenotypic characteristics of strains belonging to group 1 (14 strains) indicated that these represented a non-sucrose-assimilating variant of Shewanella baltica with a DNA G+C content of 47.0 mol%. Strains of group 2 (33 isolates) did not utilize the carbon substrates assimilated by S. baltica except gluconate, N-acetylglucosamine and malate. Their DNA G+C content was 44.0 mol%. Phylogenetic analysis of the 16S rRNA gene sequence data placed the two novel species within the genus Shewanella. Group 1 strains showed greatest sequence similarity to Shewanella putrefaciens ATCC 8071T (99.0 %) and with S. baltica NCTC 10375(T) (98.3 %). However, gyrB gene sequence analysis showed these isolates to share only 90.0 % sequence similarity with S. putrefaciens ATCC 8071T and 93.9 % with S. baltica NCTC 10375T. Similarly, DNA-DNA hybridization experiments revealed DNA relatedness levels of 38 % between the group 1 isolates and S. putrefaciens ATCC 8071T and 43 % with S. baltica NCTC 10375T. The group 2 strains shared less than 97 % 16S rRNA gene sequence similarities with recognized Shewanella species. Comparisons between the two novel species indicated 16S rRNA gene sequence similarity of approximately 98 %, gyrB gene sequence similarity of approximately 89 % and DNA-DNA reassociation values of 20-34 %. Based on the evidence presented, two novel species, Shewanella hafniensis sp. nov. (type strain P010T = ATCC BAA-1207T = NBRC 100975T) and Shewanella morhuae sp. nov. (type strain U1417T = ATCC BAA-1205T = NBRC 100978T), are described.

Animals↗

PubMed2006

Bacillus tequilensis sp. nov., isolated from a 2000-year-old Mexican shaft-tomb, is closely related to Bacillus subtilis.

A Gram-positive, spore-forming bacillus was isolated from a sample taken from an approximately 2000-year-old shaft-tomb located in the Mexican state of Jalisco, near the city of Tequila. Tentative identification using conventional biochemical analysis consistently identified the isolate as Bacillus subtilis. DNA isolated from the tomb isolate, strain 10b(T), and closely related species was used to amplify a Bacillus-specific portion of the highly conserved 16S rRNA gene and an internal region of the superoxide dismutase gene (sodA(int)). Trees derived from maximum-likelihood methods applied to the sodA(int) sequences yielded non-zero branch lengths between strain 10b(T) and its closest relative, whereas a comparison of a Bacillus-specific 546 bp amplicon of the 16S rRNA gene demonstrated 99 % similarity with B. subtilis. Although the 16S rRNA gene sequences of strain 10b(T) and B. subtilis were 99 % similar, PFGE of NotI-digested DNA of strain 10b(T) revealed a restriction profile that was considerably different from those of B. subtilis and other closely related species. Whereas qualitative differences in whole-cell fatty acids were not observed, significant quantitative differences were found to exist between strain 10b(T) and each of the other closely related Bacillus species examined. In addition, DNA-DNA hybridization studies demonstrated that strain 10b(T) had a relatedness value of less than 70 % with B. subtilis and other closely related species. Evidence from the sodA(int) sequences, whole-cell fatty acid profiles and PFGE analysis, together with results from DNA-DNA hybridization studies, justify the classification of strain 10b(T) as representing a distinct species, for which the name Bacillus tequilensis sp. nov. is proposed. The type strain is 10b(T) (=ATCC BAA-819(T)=NCTC 13306(T)).

Archaeology↗

PubMed2006

Paenibacillus pasadenensis sp. nov. and Paenibacillus barengoltzii sp. nov., isolated from a spacecraft assembly facility.

Two novel spore-forming, Gram-positive, mesophilic, heterotrophic bacteria representing two novel species were isolated from the Jet Propulsion Laboratory Spacecraft Assembly Facility (JPL-SAF) at Pasadena, CA, USA. The incidence of similar strains was examined by screening the growing collection of isolates ( approximately 400 strains) obtained from the JPL-SAF using species-specific PCR primer sets designed from the 16S rRNA gene sequences of strains SAFN-016(T) and SAFN-007(T). Phylogenetic analysis of 16S rRNA gene sequences placed these novel isolates within the genus Paenibacillus. Two strains, SAFN-016(T) and SAFN-125, shared 98 % 16S rRNA gene sequence similarity with Paenibacillus timonensis and 97 % similarity with Paenibacillus macerans. Strain SAFN-007(T) showed 95.2 % 16S rRNA gene sequence similarity with Paenibacillus kobensis, its nearest phylogenetic neighbour. The results of DNA-DNA hybridization, physiological tests and biochemical analysis allowed genotypic and phenotypic differentiation of the isolates from currently recognized Paenibacillus species. Strain SAFN-007(T) and strains SAFN-016(T) and SAFN-125 are representatives of two separate novel species, for which the names Paenibacillus pasadenensis sp. nov. (type strain SAFN-007(T)=ATCC BAA-1211(T)=NBRC 101214(T)) and Paenibacillus barengoltzii sp. nov. (type strain SAFN-016(T)=ATCC BAA-1209(T)=NBRC 101215(T)) are proposed.

Bacterial Typing Techniques↗

PubMed2006

Bacillus safensis sp. nov., isolated from spacecraft and assembly-facility surfaces.

Thirteen strains of a novel spore-forming, Gram-positive, mesophilic heterotrophic bacterium were isolated from spacecraft surfaces (Mars Odyssey Orbiter) and assembly-facility surfaces at the Jet Propulsion Laboratory in California and the Kennedy Space Center in Florida. Phylogenetic analysis of 16S rRNA gene sequences has placed these novel isolates within the genus Bacillus, the greatest sequence similarity (99.9 %) being found with Bacillus pumilus. However, these isolates share a mere 91.2 % gyrB sequence similarity with Bacillus pumilus, rendering their 16S rRNA gene-derived relatedness suspect. Furthermore, DNA-DNA hybridization showed only 54-66 % DNA relatedness between the novel isolates and strains of B. pumilus. rep-PCR fingerprinting and previously reported matrix-assisted laser desorption/ionization time-of-flight mass spectrometry protein profiling clearly distinguished these isolates from B. pumilus. Phenotypic analyses also showed some differentiation between the two genotypic groups, although the fatty acid compositions were almost identical. The polyphasic taxonomic studies revealed distinct clustering of the tested strains into two distinct species. On the basis of phenotypic characteristics and the results of phylogenetic analyses of 16S rRNA and gyrB gene sequences, repetitive element primer-PCR fingerprinting and DNA-DNA hybridization, the 13 isolates represent a novel species of the genus Bacillus, for which the name Bacillus safensis sp. nov. is proposed. The type strain is FO-36b(T) (=ATCC BAA-1126(T)=NBRC 100820(T)).

Bacillus↗

PubMed2005

Recurrent isolation of hydrogen peroxide-resistant spores of Bacillus pumilus from a spacecraft assembly facility.

While the microbial diversity of a spacecraft assembly facility at the Jet Propulsion Laboratory (Pasadena, CA) was being monitored, H2O2-resistant bacterial strains were repeatedly isolated from various surface locations. H2O2 is a possible sterilant for spacecraft hardware because it is a low-temperature process and compatible with various modern-day spacecraft materials, electronics, and components. Both conventional biochemical testing and molecular analyses identified these strains as Bacillus pumilus. This Bacillus species was found in both unclassified (entrance floors, anteroom, and air-lock) and classified (floors, cabinet tops, and air) locations. Both vegetative cells and spores of several B. pumilus isolates were exposed to 5% liquid H2O2 for 60 min. Spores of each strain exhibited higher resistance than their respective vegetative cells to liquid H2O2. Results indicate that the H2O2 resistance observed in both vegetative cells and spores is strain-specific, as certain B. pumilus strains were two to three times more resistant than a standard Bacillus subtilis dosimetry strain. An example of this trend was observed when the type strain of B. pumilus, ATCC 7061, proved sensitive, whereas several environmental strains exhibited varying degrees of resistance, to H2O2. Repeated isolation of H2O2-resistant strains of B. pumilus in a clean-room is a concern because their persistence might potentially compromise life-detection missions, which have very strict cleanliness and sterility requirements for spacecraft hardware.

Bacillus↗

PubMed2005

Identification of Shewanella baltica as the most important H2S-producing species during iced storage of Danish marine fish.

Shewanella putrefaciens has been considered the main spoilage bacteria of low-temperature stored marine seafood. However, psychrotropic Shewanella have been reclassified during recent years, and the purpose of the present study was to determine whether any of the new Shewanella species are important in fish spoilage. More than 500 H2S-producing strains were isolated from iced stored marine fish (cod, plaice, and flounder) caught in the Baltic Sea during winter or summer time. All strains were identified as Shewanella species by phenotypic tests. Different Shewanella species were present on newly caught fish. During the warm summer months the mesophilic human pathogenic S. algae dominated the H2S-producing bacterial population. After iced storage, a shift in the Shewanella species was found, and most of the H2S-producing strains were identified as S. baltica. The 16S rRNA gene sequence analysis confirmed the identification of these two major groups. Several isolates could only be identified to the genus Shewanella level and were separated into two subgroups with low (44%) and high (47%) G+C mol%. The low G+C% group was isolated during winter months, whereas the high G+C% group was isolated on fish caught during summer and only during the first few days of iced storage. Phenotypically, these strains were different from the type strains of S. putrefaciens, S. oneidensis, S. colwelliana, and S. affinis, but the high G+C% group clustered close to S. colwelliana by 16S rRNA gene sequence comparison. The low G+C% group may constitute a new species. S. baltica, and the low G+C% group of Shewanella spp. strains grew well in cod juice at 0 degrees C, but three high G+C Shewanella spp. were unable to grow at 0 degrees C. In conclusion, the spoilage reactions of iced Danish marine fish remain unchanged (i.e., trimethylamine-N-oxide reduction and H2S production); however, the main H2S-producing organism was identified as S. baltica.

Animals↗

PubMed2005

Survival of spacecraft-associated microorganisms under simulated martian UV irradiation.

Spore-forming microbes recovered from spacecraft surfaces and assembly facilities were exposed to simulated Martian UV irradiation. The effects of UVA (315 to 400 nm), UVA+B (280 to 400 nm), and the full UV spectrum (200 to 400 nm) on the survival of microorganisms were studied at UV intensities expected to strike the surfaces of Mars. Microbial species isolated from the surfaces of several spacecraft, including Mars Odyssey, X-2000 (avionics), and the International Space Station, and their assembly facilities were identified using 16S rRNA gene sequencing. Forty-three Bacillus spore lines were screened, and 19 isolates showed resistance to UVC irradiation (200 to 280 nm) after exposure to 1,000 J m(-2) of UVC irradiation at 254 nm using a low-pressure mercury lamp. Spores of Bacillus species isolated from spacecraft-associated surfaces were more resistant than a standard dosimetric strain, Bacillus subtilis 168. In addition, the exposure time required for UVA+B irradiation to reduce the viable spore numbers by 90% was 35-fold longer than the exposure time required for the full UV spectrum to do this, confirming that UVC is the primary biocidal bandwidth. Among the Bacillus species tested, spores of a Bacillus pumilus strain showed the greatest resistance to all three UV bandwidths, as well as the total spectrum. The resistance to simulated Mars UV irradiation was strain specific; B. pumilus SAFR-032 exhibited greater resistance than all other strains tested. The isolation of organisms like B. pumilus SAFR-032 and the greater survival of this organism (sixfold) than of the standard dosimetric strains should be considered when the sanitation capabilities of UV irradiation are determined.

Bacillus↗

PubMed2004

gyrB as a phylogenetic discriminator for members of the Bacillus anthracis-cereus-thuringiensis group.

Bacillus anthracis, the causative agent of the human disease anthrax, Bacillus cereus, a food-borne pathogen capable of causing human illness, and Bacillus thuringiensis, a well-characterized insecticidal toxin producer, all cluster together within a very tight clade (B. cereus group) phylogenetically and are indistinguishable from one another via 16S rDNA sequence analysis. As new pathogens are continually emerging, it is imperative to devise a system capable of rapidly and accurately differentiating closely related, yet phenotypically distinct species. Although the gyrB gene has proven useful in discriminating closely related species, its sequence analysis has not yet been validated by DNA:DNA hybridization, the taxonomically accepted "gold standard". We phylogenetically characterized the gyrB sequences of various species and serotypes encompassed in the "B. cereus group," including lab strains and environmental isolates. Results were compared to those obtained from analyses of phenotypic characteristics, 16S rDNA sequence, DNA:DNA hybridization, and virulence factors. The gyrB gene proved more highly differential than 16S, while, at the same time, as analytical as costly and laborious DNA:DNA hybridization techniques in differentiating species within the B. cereus group.

Bacillus↗

PubMed2004

MALDI-TOFMS compared with other polyphasic taxonomy approaches for the identification and classification of Bacillus pumilus spores.

To verify the efficacy of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) protein profiling for identifying and differentiating bacterial species, several strains of Bacillus pumilus were examined in a thorough taxonomic study incorporating a polyphasic approach. Sixteen isolates of putative B. pumilus isolated from spacecraft assembly facilities, the Mars Odyssey spacecraft, and the International Space Station, were characterized for their biochemical and molecular profiles using the Biolog system, DNA techniques, and MALDI-TOFMS protein profiling. MALDI-TOFMS protein profiling was more accurate than Biolog metabolic profiling, more discriminating than 16S rDNA sequence analysis, and complemented the results of gyrB sequence analysis and DNA-DNA hybridization for the identification of the B. pumilus spores. This is the first report whereby MALDI-TOFMS generated protein profiles from a set of microbes is compared directly with DNA-DNA hybridization yielding a positive correlation. Unique, cluster-specific biomarker peaks have been identified in the spores of the B. pumilus examined in this study. MALDI-TOFMS protein profiling is a rapid and simple analysis and has been demonstrated as a useful taxonomic tool for differentiating spores of the genus Bacillus. For practical purposes, it would be ideal (and necessary) to have a publicly available, standardized MALDI profile database, to facilitate the use of the technique as a diagnostic method to differentiate bacterial species.

Bacillus↗

PubMed2004

Evaluation of various cleaning methods to remove bacillus spores from spacecraft hardware materials.

A detailed study was made of the biological cleaning effectiveness, defined in terms of the ability to remove bacterial spores, of a number of methods used to clean hardware surfaces. Aluminum (Al 6061) and titanium (Ti 6Al-4V) were chosen for the study as they were deemed the two materials most likely to be used in spacecraft extraterrestrial sampler construction. Metal coupons (1 cm x 2.5 cm) were precleaned and inoculated with 5.8 x 10(3) cultivable Bacillus subtilis spores, which are commonly found on spacecraft surfaces and in the assembly environments. The inoculated coupons were subsequently cleaned using: (1) 70% isopropyl alcohol wipe; (2) water wipe; (3) multiple-solvent flight-hardware cleaning procedures used at the Jet Propulsion Laboratory (JPL); (4) Johnson Space Center-developed ultrapure water rinse; and (5) a commercial, semi-aqueous, multiple-solvent (SAMS) cleaning process. The biological cleaning effectiveness was measured by agar plate assay, sterility test (growing in liquid media), and epifluorescent microscopy. None of the cleaning protocols tested completely removed viable spores from the surface of the aluminum. In contrast, titanium was capable of being cleaned to sterility by two methods, the JPL standard and the commercial SAMS cleaning process. Further investigation showed that the passivation step employed in the JPL standard method is an effective surface sterilant on both metals but not compatible with aluminum. It is recommended that titanium (Ti 6Al-4V) be considered superior to aluminum (Al 6061) for use in spacecraft sampling hardware, both for its potential to be cleaned to sterilization and for its ability to withstand the most effective cleaning protocols.

Aluminum↗

PubMed2004

Bacillus odysseyi sp. nov., a round-spore-forming bacillus isolated from the Mars Odyssey spacecraft.

A round-spore-forming Bacillus species that produces an exosporium was isolated from the surface of the Mars Odyssey spacecraft. This novel species has been characterized on the basis of phenotypic traits, 16S rDNA sequence analysis and DNA-DNA hybridization. According to the results of these analyses, this strain belongs to the genus Bacillus and is a Gram-positive, aerobic, rod-shaped, endospore-forming eubacterium. Ultrathin sections of the spores showed the presence of an exosporium, spore coat, cortex and core. 16S rDNA sequence similarities between this strain, Bacillus fusiformis and Bacillus silvestris were approximately 96% and DNA-DNA reassociation values with these two bacilli were 23 and 17%, respectively. Spores of the novel species were resistant to desiccation, H2O2 and UV and gamma radiation. Of all strains tested, the spores of this strain were the most consistently resistant and survived all of the challenges posed, i.e. exposure to conditions of desiccation (100% survival), H2O2 (26% survival), UV radiation (10% survival at 660 J m(-2)) and gamma radiation (0.4% survival). The name proposed for this novel bacterium is Bacillus odysseyi sp. nov.; the type strain is 34hs-1T (=ATCC PTA-4993T=NRRL B-30641T=NBRC 100172T).

Bacillus↗

PubMed2004

Species differentiation of a diverse suite of Bacillus spores by mass spectrometry-based protein profiling.

In this study, we demonstrate the versatility of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOFMS) protein profiling for the species differentiation of a diverse suite of Bacillus spores. MALDI-TOFMS protein profiles of 11 different strains of Bacillus spores, encompassing nine different species, were evaluated. Bacillus species selected for MALDI-TOFMS analysis represented the spore-forming bacterial diversity of typical class 100K clean room spacecraft assembly facilities. A one-step sample treatment and MALDI-TOFMS preparation were used to minimize the sample preparation time. A library of MALDI-TOFMS spectra was created from these nine Bacillus species, the most diverse protein profiling study of the genus reported to date. Linear correlation analysis was used to successfully differentiate the MALDI-TOFMS protein profiles from all strains evaluated in this study. The MALDI-TOFMS protein profiles were compared with 16S rDNA sequences for their bacterial systematics and molecular phylogenetic affiliations. The MALDI-TOFMS profiles were found to be complementary to the 16S rDNA analysis. Proteomic studies of Bacillus subtilis 168 were pursued to identify proteins represented by the biomarker peaks in the MALDI-TOFMS spectrum. Four small, acid-soluble proteins (A, B, C, and D), one DNA binding protein, hypothetical protein ymf J, and four proteins associated with the spore coat and spore coat formation (coat JB, coat F, coat T, and spoIVA) were identified. The ability to visualize higher-molecular-mass coat proteins (10 to 25 kDa) as well as smaller proteins (<10 kDa) with MALDI-TOFMS profiling is critical for the complete and effective species differentiation of the Bacillus genus.

Bacillus↗

PubMed2004

Evidence of pathogenic microbes in the International Space Station drinking water: reason for concern?

Molecular analyses were carried out on four preflight and six postflight International Space Station (ISS)-associated potable water samples at various stages of purification, storage, and transport, to ascertain their associated microbial diversities and overall microbial burdens. Following DNA extraction, PCR amplification, and molecular cloning procedures, rDNA sequences closely related to pathogenic species of Acidovorax, Afipia, Brevundimonas, Propionibacterium, Serratia, and others were recovered in varying abundance. Retrieval of sequences arising from the iodine (biocide)-reducing Delftia acidovorans in postflight waters is also of concern. Total microbial burdens of ISS potable waters were derived from data generated by an ATP-based enumeration procedure, with results ranging from 0 to 4.9 x 10(4) cells/ml. Regardless of innate biases in sample collection and analysis, such circumstantial evidence for the presence of viable, intact pathogenic cells should not be taken lightly. Implementation of new cultivation approaches and/or viability-based assays are requisite to confirm such an occurrence.

Anti-Bacterial Agents↗

PubMed2003

ATP as a biomarker of viable microorganisms in clean-room facilities.

A new firefly luciferase bioluminescence assay method that differentiates free extracellular ATP (dead cells, etc.) from intracellular ATP (viable microbes) was used to determine the viable microbial cleanliness of various clean-room facilities. For comparison, samples were taken from both clean-rooms, where the air was filtered to remove particles >0.5 microm, and ordinary rooms with unfiltered air. The intracellular ATP was determined after enzymatically degrading the sample's free ATP. Also for comparison, cultivable microbial populations were counted on nutrient-rich trypticase soy agar (TSA) plates. Both the cultivable and ATP-based determinations indicate that the microbial burden was lower in clean-room facilities than in ordinary rooms. However, there was no direct correlation between the two sets of measurements because the two assays measured very different populations. A large fraction of the samples yielded no colony formers on TSA, but were positive for intracellular ATP. Subsequently, genomic DNA was isolated directly from selected samples and 16S rDNA fragments were cloned and sequenced, identifying nearest neighbors, many of which are known to be noncultivable in the media employed. It was concluded that viable microbial contamination can be reliably monitored by measurement of intracellular ATP, and that this method may be considered superior to cultivable colony counts due to its speed and its ability to report the presence of viable but noncultivable organisms. When the detection of nonviable microbes is of interest, the ATP assay can be supplemented with DNA analysis.

Adenosine Triphosphate↗

PubMed2003

Microbial characterization of the Mars Odyssey spacecraft and its encapsulation facility.

Microbial characterization of the Mars Odyssey spacecraft and the Kennedy Space Center Spacecraft Assembly and Encapsulation Facility II (SAEF-II) was carried out by both culture-based and molecular methods. The most dominant cultivable microbes were species of Bacillus, with comamonads, microbacteria and actinomycetales also represented. Several spore-forming isolates were resistant to gamma-radiation, UV, H2O2 and desiccation, and one Acinetobacter radioresistens isolate and several Aureobasidium, isolated directly from the spacecraft, survived various conditions. Sequences arising in clone libraries were fairly consistent between the spacecraft and facility; predominant genera included Variovorax, Ralstonia and Aquaspirillum. This study improves our understanding of the microbial community structure, diversity and survival capabilities of microbes in an encapsulation facility and physically associated with colocated spacecraft.

Actinomycetales↗

PubMed2003

Spore UV and acceleration resistance of endolithic Bacillus pumilus and Bacillus subtilis isolates obtained from Sonoran desert basalt: implications for lithopanspermia.

Bacterial spores have been used as model systems for studying the theory of interplanetary transport of life by natural processes such as asteroidal or cometary impacts (i.e., lithopanspermia). Because current spallation theory predicts that near-surface rocks are ideal candidates for planetary ejection and surface basalts are widely distributed throughout the rocky planets, we isolated spore-forming bacteria from the interior of near-subsurface basalt rocks collected in the Sonoran desert near Tucson, Arizona. Spores were found to inhabit basalt at very low concentrations (</=28 colony-forming units/g) in these samples. Six isolates identified as being most closely related to Bacillus pumilus and one Bacillus subtilis isolate were recovered from near-subsurface basalt samples. Populations of purified spores prepared from the isolated strains were subjected to 254-nm UV and ballistics tests in order to assess their resistance to UV radiation and to extreme acceleration shock, two proposed lethal factors for spores during interplanetary transfer. Specific natural isolates of B. pumilus were found to be substantially more resistant to UV and extreme acceleration than were reference laboratory strains of B. subtilis, the benchmark organism, suggesting that spores of environmental B. pumilus isolates may be more likely to survive the rigors of interplanetary transfer.

Bacillus↗

PubMed2003

Bacillus nealsonii sp. nov., isolated from a spacecraft-assembly facility, whose spores are gamma-radiation resistant.

One of the spore-formers isolated from a spacecraft-assembly facility, belonging to the genus Bacillus, is described on the basis of phenotypic characterization, 16S rDNA sequence analysis and DNA-DNA hybridization studies. It is a Gram-positive, facultatively anaerobic, rod-shaped eubacterium that produces endospores. The spores of this novel bacterial species exhibited resistance to UV, gamma-radiation, H2O2 and desiccation. The 18S rDNA sequence analysis revealed a clear affiliation between this strain and members of the low G+C Firmicutes. High 16S rDNA sequence similarity values were found with members of the genus Bacillus and this was supported by fatty acid profiles. The 16S rDNA sequence similarity between strain FO-92T and Bacillus benzoevorans DSM 5391T was very high. However, molecular characterizations employing small-subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in this genus, but DNA-DNA hybridization data support the proposal of FO-92T as Bacillus nealsonii sp. nov. (type strain is FO-92T =ATCC BAAM-519T =DSM 15077T).

Bacillus↗