RNA-Binding Domain is Necessary for PprM Function in Response to the Extreme Environmental Stress in <Emphasis Type="Italic">Deinococcus radiodurans</Emphasis>

Deinococcus radiodurans was considered as one of the most radiation-resistant organisms on Earth because of its strong resistance to the damaging factors of both DNA and protein, including ionizing radiation, ultraviolet radiation, oxidants, and desiccation. PprM, as a bacterial cold shock protein homolog, was involved in the radiation resistance and oxidative stress response of D. radiodurans, but its potential mechanisms are poorly expounded. In this study, we found that PprM was highly conserved with the RNA-binding domain in Deinococcus genus through performing phylogenic analysis. Moreover, the paper presents the analysis on the tolerance of environmental stresses both in the wild-type and the pprM/pprM RBD mutant strains, demonstrating that pprM and RNA-binding domain disruptant strain were with higher sensitivity than the wild-type strain to cold stress, mitomycin C, UV radiation, and hydrogen peroxide. In the following step, the recombinant PprM was purified, with the finding that PprM was bound to the 5’-untranslated region of its own mRNA by gel mobility shift assay in vitro. With all these findings taken into consideration, it was suggested that PprM act as a cold shock protein and its RNA-binding domain may be involved in reaction to the extreme environmental stress in D. radiodurans.     

The fine structure of micrococcus radiodurans

Summary The fine structure of the radiation-resistant bacterium, Micrococcus radiodurans, isolated by Anderson, was studied by electron microscopy of intact and disrupted cells using thin sectioning and negative staining techniques. The cytoplasm and nuclear structures are normal, but the cell wall and sheath are more complex than any so far described for a bacterium. The surface consists of four distinct layers, each having a characteristic fine structure, one of which has been tentatively identified as that responsible for maintaining the rigidity of the cells. Striations with a periodicity of 175 to 200 Å are visible in thin sections of this layer, and a pseudo-hexagonal array of dark holes is seen in surface view of negatively-stained fragments. It is concluded that this layer is the main structural element of the cell wall of M. radiodurans. The other three layers of the surface have not been clearly located in thin sections; one of these layers has a well-defined pattern of hexagonally arranged units similar to that observed in Spirillum serpens by Murray but with different dimensions.Sir Halley Stewart Research Fellow.     

Defective excision repair in a mutant of Micrococcus radiodurans hypermutable by some monofunctional alkylating agents

Summary The lethal and mutagenic effects of methyl methanesulphonate (MMS), ethyl methanesulphonate (EMS), and N-methyl-N-nitro-N-nitrosoguanidine (MNNG) can be dissociated in a mitomycin C (MTC)-sensitive mutant, strain 302, of Micrococcus radiodurans.As regards lethality 302 is extremely sensitive, compared with the wild type, to MTC and decarbamoyl MTC (DCMTC), slightly sensitive to EMS, MNNG, nitrous acid, 7-bromomethylbenz {} anthracene (BrMBA), and N-acetoxy-N-2-acetylaminofluorene (AAAF), and resistant to MMS, hydroxylamine, and ICR 191G. As regards mutability it is, compared to the wild type, very sensitive to MMS, EMS, and MNNG, and slightly sensitive to hydroxylamine and nitrous acid but not to any other agent examined.Alkaline sucrose gradient studies indicate that 302 does not incise DNA containing BrMBA adducts, although it does incise DNA damaged by AAAF but probably not to the same extent as wild type.We put forward the hypothesis that the hypermutability of 302 is due to the non-removal of bases or nucleotides, modified in exocyclic positions, which have altered base-pairing capabilities, while lethality results from the non-removal of bases or nucleotides, also modified in exocyclic positions, which no longer form hydrogen-bonded base pairs.     

DNA repair in the extremely radioresistant bacterium Deinococcus radiodurans

Deinococcus radiodurans and other members of the same genus share extraordinary resistance to the lethal and mutagenic effects of ionizing and u.v. radiation and to many other agents that damage DNA. While it is known that this resistance is due to exceedingly efficient DNA repair, the molecular mechanisms responsible remain poorly understood. Following very high exposures to u.v. irradiation (e.g. 500 Jm⁻², which is non-lethal to D. radiodurans), this organism carries out extremely efficient excision repair accomplished by two separate nucleotide excision repair pathways acting simultaneously. One pathway requires the uvrA gene and appears similar to the UvrABC excinuclease pathway defined in Escherichia coli. The other excision repair pathway is specific for u.v. dimeric photoproducts, but is not mediated by a pyrimidine dimer DNA glycosylase. Instead, it is initiated by a second bona fide endonuclease that may recognize both pyrimidine dimers and pyrimidine-(6–4)pyrimidones. After high doses of ionizing-radiation (e.g. 1.5Mrad), D. radiodurans can mend >100 double-strand breaks (dsb) per chromosome without lethality or mutagenesis. Both dsb mending and survival are recA-dependent, indicating that efficient dsb mending proceeds via homologous recombination. D. radiodurans contains multiple chromosomes per cell, and it is proposed that dsb mending requires extensive recombination amongst these chromosomes, a novel phenomenon in bacteria. Thus, D. radiodurans may serve as an easily accessible model system for the double-strand-break-initiated interchromosomal recombination that occurs in eukaryotic cells during mitosis and meiosis.     

Ring-like nucleoid does not play a key role in radioresistance of Deinococcus radiodurans

The conclusion based on transmission electron microscopy, “the tightly packed ring-like nucleoid of the Deinococcus radiodurans R1 is a key to radioresistance”, has instigated lots of debates. In this study, according to the previous research of Pprl’s crucial role in radioresistance of D. radiodurans, we have attempted to examine and compare the nucleoid morphology differences among wild-type D. radiodurans R1 strain, pprf function-deficient mutant (YR1), and pprl function-complementary strains (YR1001, YR1002, and YR1004) before and after exposure to ionizing irradiation. Fluorescence microscopy images indicate: (1) the majority of nucleoid structures in radioresistant strain R1 cells exhibit the tightly packed ring-like morphology, while the pprl function-deficient mutant YR1 cells carrying predominate ring-like structure represent high sensitivity to irradiation; (2) as an extreme radioresistant strain similar to wild-type R1, pprl completely function-complementary strain YR1001 almost displays the loose and irregular nucleoid morphologies. On the other hand, another radioresistant pprl partly function-complementary strain YR1002’s nucleiods exhibit about 60% ring-like structure; (3) a Pprl C-terminal deletion strain YR1004 consisting of approximately 60% of ring-like nucleoid is very sensitive to radiation. Therefore, our present experiments do not support the conclusion that the ring-like nucleoid of D. radiodurans does play a key role in radioresistance. Supported by the National Basic Research Program of China (Grant No. 2004CB19604), the National Natural Science Foundation of China (Grant No. 30330020), and the National Science fund for Distinguished Young Scholars (Grant No. 30425038)     

Photoinhibition of photosynthesis represents a mechanism for the long-term regulation of photosystem II

The obligate shade plant, Tradescantia albiflora Kunth grown at 50 mol photons · m^–2 s^–1 and Pisum sativum L. acclimated to two photon fluence rates, 50 and 300 mol · m^–2 · s^–1, were exposed to photoinhibitory light conditions of 1700 mol · m^–2 · s^–1 for 4 h at 22° C. Photosynthesis was assayed by measurement of CO₂-saturated O₂ evolution, and photosystem II (PSII) was assayed using modulated chlorophyll fluorescence and flash-yield determinations of functional reaction centres. Tradescantia was most sensitive to photoinhibition, while pea grown at 300 mol · m^–2 · s^–1 was most resistant, with pea grown at 50 mol · m^–2 · s^–1 showing an intermediate sensitivity. A very good correlation was found between the decrease of functional PSII reaction centres and both the inhibition of photosynthesis and PSII photochemistry. Photoinhibition caused a decline in the maximum quantum yield for PSII electron transport as determined by the product of photochemical quenching (q_p) and the yield of open PSII reaction centres as given by the steady-state fluorescence ratio, F_vF_m, according to Genty et al. (1989, Biochim. Biophys. Acta 990, 81–92). The decrease in the quantum yield for PSII electron transport was fully accounted for by a decrease in F_vF_m, since q_p at a given photon fluence rate was similar for photoinhibited and noninhibited plants. Under lightsaturating conditions, the quantum yield of PSII electron transport was similar in photoinhibited and noninhibited plants. The data give support for the view that photoinhibition of the reaction centres of PSII represents a stable, long-term, down-regulation of photochemistry, which occurs in plants under sustained high-light conditions, and replaces part of the regulation usually exerted by the transthylakoid pH gradient. Furthermore, by investigating the susceptibility of differently lightacclimated sun and shade species to photoinhibition in relation to q_p, i.e. the fraction of open-to-closed PSII reaction centres, we also show that irrespective of light acclimation, plants become susceptible to photoinhibition when the majority of their PSII reaction centres are still open (i.e. primary quinone acceptor oxidized). Photoinhibition appears to be an unavoidable consequence of PSII function when light causes sustained closure of more than 40% of PSII reaction centres.Abbreviations F_o and F_o minimal fluorescence when all PSII reaction centres are open in darkness and steady-state light, respectively - F_m and F_m maximal fluorescence when all PSII reaction centres are closed in darkand light-acclimated leaves, respectively - F_v variable fluorescence - (F_m-F_o) under steady-state light con-ditions - F_s steady-state fluorescence in light - Q_A the primary,stable quinone acceptor of PSII - q_Ne non-photochemical quench-ing of fluorescence due to high energy state - (pH); q_Ni non-photochemical quenching of fluorescence due to photoinhibition - q_p photochemical quenching of fluorescence To whom correspondence should be addressedThis work was supported by the Swedish Natural Science Research Council (G.Ö.) and the award of a National Research Fellowship to J.M.A and W.S.C. We thank Dr. Paul Kriedemann, Division of Forestry and Forest Products, CSIRO, Canberra, Australia, for helpful discussions.     

Expression,purification, characterization,and deletion mutations of phosphorylase kinase γ subunit: identification of an inhibitory domain in the γ subunit

A catalytic fragment, _1-298, derived from limited chymotryptic digestion of phosphorylaseb kinase (Harris, W.R.et al., J. Biol. Chem., 265: 11740–11745, 1990), is reported to have about six-fold greater specific activity than does the subunit-calmodulin complex. To test whether there is an inhibitory domain located outside the catalytic core of the subunit, full-length wild-type and seven truncated forms of were expressed inE. coli. Recombinant proteins accumulate in the inclusion bodies and can be isolated, solubilized, renatured, and purified further by ammonium sulfate precipitation and Q-Sepharose column. Four out of seven truncated mutants show similar ( _1-353 and _1-341) or less ( _1-331 and _1-276) specific activity than does the full-length wild-type , _1-386. Three truncated forms, _1-316, _1-300, and _1-290 have molar specific activities approximately twice as great as those of the full-length wild-type and the nonactivated holoenzyme. All recombinant s exhibit similarK _m values for both substrates, i.e., about 18M for phosphorylaseb and about 75 M for MgATP. Three truncated s, _1-316, _1-300, and _1-290, have a 1.9- to 2.5-fold greater catalytic efficiency (V _max/K _m) than that of the full-length wild-type and a 3.5- to 4.5-fold greater efficiency than that of the truncated _1-331. This evidence suggests that there is at least one inhibitory domain in the C-terminal region of , which is located at _301-331· _1-290, but not _1-276, which contains the highly conserved kinase domain, is the minimum sequence required for the subunit to exhibit phosphotransferase activity. Both _1-290 and _1-300 have several properties similar to full-length wild-type , including metal ion responses (activation by free Mg²⁺ and inhibition by free Mn²⁺) pH dependency, and substrate specificities.     

Roles of PprA,IrrE, and RecA in the resistance of <Emphasis Type="Italic">Deinococcus radiodurans</Emphasis> to germicidal and environmentally relevant UV radiation

To study the role of different DNA repair genes in the resistance of Deinococcus radiodurans to mono- and polychromatic UV radiation, wild-type strain and knockout mutants in RecA, PprA, and IrrE of D. radiodurans were irradiated with UV-C (254 nm), UV-(A + B) (280–400 nm) and UV-A (315–400 nm) radiation, and survival was monitored. The strain deficient in recA was highly sensitive to UV-C radiation compared to the wild-type, but showed no loss of resistance against irradiation with UV-(A + B) and UV-A, while pprA and irrE-deficient strains exhibited elevated sensitivity to UV-A and UV-(A + B) radiation. These results suggest that the repair of DNA double-strand breaks is essential after treatment with highly energetic UV-C radiation, whereas protection from oxidative stress may play a greater role in resistance to environmentally relevant UV radiation.     

A Paecilomyces fumosoroseus mutant over-producing chitinase displays enhanced virulence against Bemisia tabaci

A Paecilomyces fumosoroseus strain was mutagenized by u.v. Among 200 colonies, one mutant (M84), showed a large and stable chitin hydrolysis-halo. Glucose consumption and biomass production were similar for M84 and the parental strain. Chitinase was inducible by chitin and repressed by glucose in both strains but, when they were grown on minimal medium plus colloidal chitin as sole carbon source, the parental and M84 strains yielded 198 and 690 mol N-acetylglucosamine, respectively. This results indicate that the mutant strain synthesized a chitinase with a higher activity. Bioassays against Bemisia tabaci nymph, showed that M84 incited a 2-fold higher incidence of disease compared to the parental strain.     

Role of ω-3 fatty acid desaturases in the regulation of the level of trienoic fatty acids during leaf cell maturation

Trienoic fatty acids, namely -linolenic acid and hexadecatrienoic acid, present in leaf lipids are produced by -3 fatty acid desaturases located in the endoplasmic reticulum and plastid membranes. The changes in the level of trienoic fatty acids during leaf maturation were investigated in wild-type plants of Arabidopsis thaliana (L.) Heynh. and in the fad7 mutant deficient in the activity of a plastid -3 desaturase. The levels of trienoic fatty acids increased in 26 °C- and 15 °C-grown wild-type plants with maturation of leaves. The increase in trienoic fatty acids was mainly due to galactolipids enriched in plastid membranes. In addition, the relative levels of trienoic fatty acids in major glycerolipids, including phospholipids enriched in the endoplasmic reticulum membranes, also increased with leaf maturation. By contrast, when the fad7 mutant was grown at 26 °C, the relative levels of trienoic fatty acids in individual lipids decreased with leaf maturation. The decreases in the levels of trienoic fatty acids, however, were alleviated when the fad7 mutant was grown at 15 °C. These results suggest that the plastid -3 desaturase plays a major role in increasing the levels of trienoic fatty acids with leaf maturation.Abbreviations 163 hexadecatrienoic acid - 183 -linolenic acid - DGD digalactosyldiacylglycerol - MGD monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - TA trienoic fatty acid - WT wild type - -3 refers to the position of the double bond from the methyl end of a fatty acid This research was supported in part by Grants-in-Aid for Scientific research (#07251214 and #06804050 to K.I.) from the Ministry of Education, Science and Culture, Japan, and by the research grant from Shorai Foundation.     

A survey of the response of Rhododendron to in vitro culture

The responses of 7 genotypes of Rhodendron to culture conditions and their establishment as shoot cultures are described. The genotypes represent a broad genetic diversity in the genus. After sterilization and an acclimation period of 3 to 12 months, all the selections were established as shoot cultures on Woody Plant Medium (WPM) supplemented with N⁶(-²-isopenteny) adenine (2iP). Plants with strong episodic growth cycles required the longer acclimation periods. Utilizing shoots from these cultures, the response to a cytokinin series of 0 to 32 M 2iP or BAP (6-Benzylaminopurine) was analyzed. BAP proved toxic to all but the elipidote and lepidote rhododendrons (R. mucronulatum, R. x Boule de Neige, and R. x PJM); however, even with these selections, 2iP stimulated greater shoot multiplication rates. The optimum 2iP level for shoot multiplication varied little with the genotype and levels of 4 to 16 M generally proved optimal, depending on the specific selection. Adventitious shoot production was observed in 3 selections (R. canadense, R. x Boule de Neige and R. x PJM), but only at 2iP levels above 8 M. Shoot multiplication rates of 7 to 21 times were observed, depending on the selection. Using an average utilizable shoot production rate of 40 shoots per culture per 6 week subculture period, some 75,000 shoots can be generated per square meter of culture space per year. The harvested shoots (microcuttings) rooted readily out-of-culture and the resultant plants grew like seedlings.     

An artificial bifunctional enzyme, γ-glutamyl kinase/γ-glutamyl phosphate reductase, improves NaCl tolerance when expressed in Escherichia coli

Summary An artificial bifunctional enzyme, -glutamyl kinase/-glutamyl phosphate reductase, was obtained by fusing the Escherichia coli genes proA and proB. The proB gene was fused to the 5-end of the proA gene with a linker encoding five amino acids. When expressed in E. coli enhanced intracellular concentrations of proline were observed. At 0.6 M NaCl the growth rates for the strain carrying the fusion enzyme and a control harbouring a plasmid encoding the wild-type enzymes were 320 and 530 min, respectively.     

Glycogen and other soluble glucans from chytridiomycete and oomycete species

Dry weight, protein, lipid, and glycogen were determined at various times during cultivation of the Chytridiomycetes, Rhizophydium sphaerotheca and Monoblepharella elongata. M. elongata had relatively stable levels of glycogen, but, in R. sphaerotheca, glycogen levels showed significant changes, particularly in older cultures in which a depletion of glycogen was accompanied by a marked thickening of the cell walls. Glycogen was a significant cellular constitutent in both chytridiomycete species. In R. sphaerotheca and M. elongata, respectively, glycogen accounted for as much as 6% and 8.1% of the dry weight. In purified glycogens of both species, only -1,4-and -1,6-linked glucosyl residues were detected and the absorbance spectra of I₂-complexes were similar to those of other well characterized glycogens. Purified Rhizophydium glycogen had a -amylolysis limit of 43%, and a of approximately 12. For the Monoblepharella polysaccharide, the respective values were 45% and 11. In extracts of the Oomycetes, Pythium debaryanum, Mindeniella spinospora, and Apodachlya sp., only -1,3- and -1,6-linked glucosyl residues were detected. These glucans were not iodophilic nor were they sensitive to -amylase and -amylase. The properties of the oomycete polysaccharides suggested that they were similar to the mycolaminarans of Phytophthora spp. Although both investigated chytridiomycete species produced glycogen with typical properties, glycogen was apparently absent in the investigated Oomycetes.     

The activity of a model heterologous protein in pep4-3 mutants of Saccharomyces cerevisiae

Summary The bacterial lacZ gene was introduced into two sibling strains of Saccharomyces cerevisiae, one a wild-type strain with normal proteinase activity and the other a pep4-3 mutant strain. The pep4-3 mutation resulted in 90% reduced activity of the four major vacuolar proteinases. By comparing the activity of the lacZ gene product (-galactosidase) in both strains the degradative effect of the major vacuolar proteinases on a heterologous protein was estimated. The mutant strain with reduced proteinase activity had higher -galactosidase activity under all the test conditions. In the most productive case the pep4-3 mutant had 55% higher -galactosidase activity than the wild-type. Batch cultures of the two strains were evaluated for growth characteristics. The strain with reduced proteinase activity grew to higher optical densities than the wild-type. Upon further examination it was found that not only were the optical densities of pep4-3 cultures greater but the cell numbers were much greater than expected due to the smaller size of pep4-3 cells. It is concluded that the strain lacking vacuolar proteinases maintained increased levels of -galactosidase and is physiologically as healthy as the wild-type.Offprint requests to: J. M. Wingfield     

Knockout of crtB or crtI gene blocks the carotenoid biosynthetic pathway in Deinococcus radiodurans R1 and influences its resistance to oxidative DNA-damaging agents due to change of free radicals scavenging ability

Deinococcus radiodurans R1, a red-pigmented strain of the extremely radioresistant genus Deinococcus, contains a major carotenoid namely deinoxanthin. The high resistance of this organism against the lethal actions of DNA-damaging agents including ionizing radiation and ultraviolet light (UV) has been widely reported. However, the possible antioxidant role of carotenoids in this strain has not been completely elucidated. In this study, we constructed two colorless mutants by knockout of crtB and crtI genes, respectively. Comparative analysis of the two colorless mutants and the wild type showed that the two colorless mutants were more sensitive to ionizing radiation, UV, and hydrogen peroxide, but not to mitomycin-C (MMC). With electron spin resonance (ESR) and spin trapping techniques, we observed that hydroxyl radical signals occurred in the suspensions of UV irradiated Deinococcus radiodurans cells and the intensity of signals was influenced by carotenoids levels. We further showed that the carotenoid extract from the wild type could obviously scavenge superoxide anions generated by the irradiated riboflavin/EDTA system. These results suggest that carotenoids in D. radiodurans R1 function as free radical scavengers to protect this organism against the deleterious effects of oxidative DNA-damaging agents.     

The resistances of Micrococcus radiodurans to killing and mutation by agents which damage DNA

The resistance of Micrococcus radiodurans to the lethal and mutagenic action 3f ultraviolet (UV) light, ionising (γ) radiation, mitomycin C (MTC), nitrous acid (NA), hydroxylamine (HA), N-methyl-N′-nitro-N-nitrosoguanidine (NG), ethylmethanesulphonate (EMS) and β-propiolactone (βPL) has been compared with that of Escherichia coli B/r.M. radiodurans was much more resistant than E. coli B/r to the lethal effects of UV light (by a factor of 33), γ-radiation (55), NG (15) and NA (62), showed intermediate resistance to MTC (4) and HA(7), but was sensitive to EMS (1) and βPL (2). M. radiodurans was very resistant to mutagens producing damage which can be repaired by a recombination system, indicating that it possesses an extremely efficient recombination repair mechanism.Both species were equally sensitive to mutation to trimethoprim resistance by NG, but M. radiodurans was more resistant the E. coli B/r to the other multagens tested, being non-mutable by UV light, γ-radiation, MTC and HA, and only slightly sensitive to mutation by NA, EMS, and βPL. The resistance of M. radiodurans to mutation by UV-light, γ-radiation and MTC is consistent with an hypothesis that recombination repair in M. radiodurans is accurate since these mutagens may depend on an “error-prone” recombination system for their mutagenic effect in E. coli B/r. However, because M. radiodurans is also resistant to mutagens such as HA and EMS, which are mutagenic in E. coli in the absence of an “error-prone” system, we propose that all the mutagens tested may have a common mode of action in E. coli B/r, but that this mutagenic pathway is missing in M. radiodurans.     

Evolution of the rabbit immunoglobulin κ chain genes

We have analyzed the organization and the structure of rabbit chain genes encoding b allotypes in wild rabbits. The 1 gene of the b95 allotype was cloned and its structure determined. The J region is composed of five segments but only J2 appears to be functional and is identical to the J2 segment of the b4 allotype. The J region is highly conserved among the various b allotypes, whereas the constant region exon displays a high level of differences when compared with other allotypes (9%–30% of different amino acids). The b95 J region is closer to that of b4^var and the constant region to b5 allotype constant region. Alignment of nucleotide sequences revealed that the constant region exon displays segmental similarities with b4 and bas constant regions. The mosaic structure of b95 allotype gene indicates that complex allotypes of 1 genes may result from genetic exchanges of gene conversion between the different genes.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide database and have been assigned the accession number M22542. Address correspondence and offprint requests to: P.-A. Cazenave.     

Random mutagenesis and use of 2-deoxy-D-glucose as an antimetabolite for selection of α-amylase-overproducing mutants of Aspergillus oryzae

By using 2-deoxy-D-glucose, selection of different mutants of Aspergillus oryzae PTCC 5164, which were produced by random mutagenesis by u.v. radiation, nitrous acid and N-methyl-N-nitro-N-nitrosoguanidine (MNNG), was studied. 2-Deoxy-D-glucose, a well-known antimetabolite, was used to isolate derepressed mutants. The mutational and lethal effects of these mutagens on conidia of A. oryzae were compared and the frequency distribution of isolated mutants, in the presence of 2-deoxy-D-glucose, was determined. Potent mutants, which produced higher dextrinizing and saccharogenic activities, were isolated. The best strain was a result of mutagenesis by nitrous acid, which produced 6.73 times more dextrinizing and 5.13 times more saccharogenic activity than the parent strain. In general, the mutants obtained by nitrous acid and u.v. were more potent than those obtained by MNNG.     

The Effect of γ-Radiation and Desiccation on the Viability of the Soil Bacteria Isolated from the Alienated Zone around the Chernobyl Nuclear Power Plant

Methylobacterium extorquens, M. mesophilicum, and Bacillus subtilis strains were found to be resistant to -radiation, irrespective of whether they were isolated from the alienated zone around the Chernobyl Nuclear Power Plant or outside this zone. The LD₉₀ of Methylobacterium and B. subtilis strains with respect to -radiation was 2.0–3.4 and 3.7–4.4 kGy, respectively, whereas their LD_99.99 values were 4.5–6.9 and more than 10 kGy, respectively. The high threshold levels of -radiation for Methylobacterium and B. subtilis imply the efficient functioning of DNA repair systems in these bacteria. Unlike Bacillus polymyxa cells, the cells of M. extorquens, M. mesophilicum, and B. subtilis were also resistant to desiccation. Pseudomonas sp., Nocardiasp., and nocardioform actinomycetes were sensitive to both -radiation and desiccation. Similar results were obtained when the bacteria studied were exposed to hydrogen peroxide and ultraviolet radiation. The results obtained indicate that the bacteria that are resistant to -radiation are also resistant to desiccation, UV radiation, and hydrogen peroxide. The possibility of using common laboratory tests (such as the determination of bacterial resistance to UV light and desiccation) for the evaluation of bacterial resistance to -radiation is discussed.