Quantitative Ecology of Psychrophilic Microorganisms

To obtain information on the importance of psychrophiles in nature, 95 samples of soil, water, mud, and various foods were quantitatively assayed for their content of psychrophilic bacteria and fungi and also for mesophilic and thermophilic bacteria and fungi. Thousands to millions of psychrophilic bacteria were present per gram of soil and represented 0.5 to 86% of the bacterial population. Also, about 25% of the fungi in uncultivated soil were psychrophilic. In stream and river water, psychrophilic bacteria constituted 16 to 47% of the bacterial population; in lake water, 41 to 76%; and in lake mud, 11 to 33%. Large numbers of psychrophilic bacteria were present in dairy products, meats, and other foods, and accounted for 35 to 93% of the bacterial population of meats. In contrast, thermophilic bacteria usually comprised 1% or less of the bacterial population in all of the materials examined. The data indicate that psychrophiles are both ubiquitous and numerous in nature, and probably play important roles in the cycles of matter.     

Influence of clay minerals,humic acid and bacterial capsular polysaccharide on the survival of Klebsiella aerogenes exposed to drying and heating in soils

The influence of clay minerals, humic acid and capsular polysaccharide on the survival of Klebsiella aerogenes exposed to drying and heating in soils was investigated. The study of three types of soils showed that the survival of the bacteria was higher in montmorillonitic than in kaolinitic soils. When a sandy soil was amended with 10 per cent montmorillonite, 10 per cent kaolinite or 0.5 per cent humic acid, the survival of K. aerogenes was increased in the presence of montmorillonite but was not affected by kaolinite or humic acid. It was suggested that montmorillinite affected the pattern of water retention by the cells during the drying process. The influence of capsular polysaccharides was also investigated and no significant difference was abserved between the survival of the encapsulated and non-capsulated strains of K. aerogenes exposed to drying and heating in soils. re]19750321     

Activity of microorganisms decomposing cholesterol]

The rates of cholesterol decomposition was compared among cell suspensions of different microorganisms. Fifty seven cultures were studied: 2 strains of actinomycetes, 23 strains of proactinomycetes, 22 strains of mycobacteria, and 10 strains of bacteria. During four hours of incubation, 11 strains virtually did not decompose cholesterol at all, 10 strains decomposed it by up to 20 per cent, 21 strains by 20 to 70 per cent, and 15 strains by 70 to 100 per cent. The highest activity was displayed by Mycobacterium rubrum 297 and Mycobacterium sp. 2B, which decomposed all cholesterol in the sample within 4 hours. The high activity was also displayed by Proactinomyces sp. 2006, Nocardia opaca JMET 7030, and Nacardia erythropolis JMET 7252.     

Isolation and characterization of psychrophiles producing cold-active beta-galactosidase

AIMS: The present study was conducted to screen for psychrophilic micro-organisms that are able to hydrolyse lactose at low temperature, and to examine the cold-active beta-galactosidase produced by the isolated psychrophilic micro-organisms. METHODS AND RESULTS: Psychrophilic bacteria, which grow on lactose as a sole carbon source, were isolated from soil from Hokkaido, Japan. The phenotype and sequence of 16S rDNA of the isolated strains indicated a taxonomic affiliation to Arthrobacter psychrolactophilus. The isolated A. psychrolactophilus strains were able to grow on lactose at below 5 degrees C, and showed cold-active beta-galactosidase activity, which was highly specific at even 0 degrees C. CONCLUSIONS: Facts in this study may indicate the possibility that the isolated strains produce novel beta-galactosidases that are able to hydrolyse lactose at low temperature, although some strains have isozymes. SIGNIFICANCE AND IMPACT OF THE STUDY: It may be possible that the cold active beta-galactosidases from the isolated strains can be applied to the food industry, e.g. processing of milk and whey below 5 degrees C.     

Types and properties of some bacteria isolated from hypersaline soils

Five rhizosphere soil samples from the dominant xerophytic plants, and nearby root-free soil samples were obtained from a series of hypersaline soils (5.0–10.7% NaCl) from sites near Alicante in Spain. Physico-chemical analyses were made, and the bacterial flora estimated using three different plating media. Counts from rhizosphere soil were always significantly higher than those from root-free soils. A total of 211 strains isolated were purified and identified to genus level; 12 could not be classified. The range of salt concentration allowing growth was determined for each isolate, but this did not correlate with the salt content of the soil habitat. Most isolates appeared to be typical moderate halophiles (with optimum growth between 5 and 15% salts), but about half of them grew on normal media with only 0.9% naCl, a notable difference from moderately halophilic aquatic bacteria. Extreme halophiles were rare but this may have been due to an insufficient incubation period.     

The effect of sodium chloride and sulphate on sulphur oxidation in soil

Summary The effect of sodium chloride on sulphur oxidation in Terra Rossa and Rendzina soils was studied by incubation and perfusion techniques. Sulphur oxidation was observed at concentrations up to 8 per cent NaCl, but was completely arrested at 10 per cent sodium chloride. Sodium chloride caused a delay in the onset of sulphur oxidation, its rate being only slightly affected. A relationship between sulphate appearance and decrease in pH was observed only in sulphur-amended Terra Rossa soil. Under optimal conditions, 53 and 54 per cent of added sulphur (5000 ppm) was recovered as SO₄-S from the Terra Rossa and Rendzina soils, respectively. This maximal level of sulphate production was only slightly affected by the addition of sulphate up to 3000 ppm S.It was concluded that inhibition in further sulphur oxidation was not caused by sulphate accumulation.     

Influence of temperature on the growth potential of Southern polar marine bacteria

Regular surveys of heterotrophic microflora from seawater were conducted in the subantarctic (Kerguelen archipelago) and Antarctic (Terre Adélie area). Although a predominance of psychrophilic bacteria could be expected for such polar marine environments, there were no significant differences between results obtained after incubation at two different temperatures (4°C for 21 days or 18°C for 6 days). To investigate this further, four sets of bacterial strains were isolated from the subantarctic area (early fall, late fall, spring, and summer) and one set of Antarctic bacteria was isolated in summer. The growth rates of the 143 strains collected were determined at four different temperatures (4, 7, 20, and 30°C). The results clearly indicated that a large majority of the isolated bacteria must be considered psychrotrophic and not truly psychrophilic strains.     

Survival of Cowpea Rhizobia in Soil as Affected by Soil Temperature and Moisture

Successful inoculation of peanuts and cowpeas depends on the survival of rhizobia in soils which fluctuate between wide temperature and moisture extremes. Survival of two cowpea rhizobial strains (TAL309 and 3281) and two peanut rhizobial strains (T-1 and 201) was measured in two soils under three moisture conditions (air-dry, moist (−0.33 bar), and saturated soil) and at two temperatures (25 and 35°C) when soil was not sterilized and at 40°C when soil was sterilized. Populations of rhizobia were measured periodically for 45 days. The results in nonsterilized soil indicated that strain 201 survived relatively well under all environmental conditions. The 35°C temperature in conjunction with the air-dry or saturated soil was the most detrimental to survival. At this temperature, the numbers of strains T-1, TAL309, and 3281 decreased about 2 logs in dry soil and 2.5 logs in saturated soil during 45 days of incubation. In sterilized soil, the populations of all strains in moist soil increased during the first 2 weeks, but decreased rapidly when incubated under dry conditions. The populations did not decline under saturated soil conditions. From these results it appears that rhizobial strains to be used for inoculant production should be screened under simulated field conditions for enhanced survival before their selection for commercial inoculant production.     

Diversity and association of psychrophilic bacteria in Antarctic sea ice.

The bacterial populations associated with sea ice sampled from Antarctic coastal areas were investigated by use of a phenotypic approach and a phylogenetic approach based on genes encoding 16S rRNA (16S rDNA). The diversity of bacteria associated with sea ice was also compared with the bacterial diversity of seawater underlying sea ice. Psychrophilic (optimal growth temperature, < or = 15 degrees C; no growth occurring at 20 degrees C) bacterial diversity was found to be significantly enriched in sea ice samples possessing platelet and bottom ice diatom assemblages, with 2 to 9 distinct (average, 5.6 +/- 1.8) psychrophilic taxa isolated per sample. Substantially fewer psychrophilic isolates were recovered from ice cores with a low or negligible population of ice diatoms or from under-ice seawater samples (less than one distinct taxon isolated per sample). In addition, psychrophilic taxa that were isolated from under-ice seawater samples were in general phylogenetically distinct from psychrophilic taxa isolated from sea ice cores. The taxonomic distributions of psychrotrophic bacterial isolates (optimal growth temperature, > 20 degrees C; growth can occur at approximately 4 degrees C) isolated from sea ice cores and under-ice seawater were quite similar. Overall, bacterial isolates from Antarctic sea ice were found to belong to four phylogenetic groups, the alpha and gamma subdivisions of the Proteobacteria, the gram-positive branch, and the Flexibacter-Bacteroides-Cytophaga phylum. Most of the sea ice strains examined appeared to be novel taxa based on phylogenetic comparisons, with 45% of the strains being psychrophilic. 16S rDNA sequence analysis revealed that psychrophilic strains belonged to the genera Colwellia, Shewanella, Marinobacter, Planococcus, and novel phylogenetic lineages adjacent to Colwellia and Alteromonas and within the Flexibacter-Bacteroides-Cytophaga phylum. Psychrotrophic strains were found to be members of the genera Pseudoalteromonas, Psychrobacter, Halomonas, Pseudomonas, Hyphomonas, Sphingomonas, Arthrobacter, Planococcus, and Halobacillus. From this survey, it is proposed that ice diatom assemblages provide niches conducive to the proliferation of a diverse array of psychrophilic bacterial species.     

塔里木盆地荒漠盐碱生境嗜盐碱细菌的初步研究

为了探索塔里木盆地荒漠盐碱生境嗜（耐）盐碱细菌的分离方法,采用纯培养技术探讨了不同土壤预处理方法、盐度及不同分离培养基对不同盐度土壤中嗜（耐）盐碱细菌分离效果的影响。结果表明：高盐土壤嗜（耐）盐碱细菌的多样性高于中度盐分和低度盐分的土壤,而总菌落数则相反;半量的Horikoshi I（NaCl 10％～15％）为3种土样最佳的分离培养基,碱性复合培养基和高盐碱培养基A次之;分离嗜（耐）盐碱细菌以获得资源为主要目的时,富集培养法最佳。以反映土壤嗜（耐）盐碱细菌生态分布而言,用土壤悬液法;塔里木盆地嗜（耐）盐碱细菌生长盐浓度及pH值范围较宽,最适生长盐浓度为10％左右,pH值多为8—10左右。分离到的120株嗜（耐）盐碱细菌中,有33株为嗜盐碱细菌,占分离菌株的27．5％。     

Directed isolation of Micromonospora generic cultures from moist soils and silts

The data on the study of various soils and substrates for isolation of Micromonospora from them are presented. It was shown that Micromonospora predominated in moist soils and especially in such substrates as silts where their content with respect to the all actinomycetous isolates amounted to 88.9 per cent. In the silts the content of Micromonospora amounted to 66.6--83 per cent, in the sopromely its content was 66 per cent, while in the ordinary non-moist soil its content was from 6 to 11 per cent. Predominance of Micromonospora in silts and moist soils makes its directed search possible.     

Mineralization of nitrogen in two soil-organic-matter fractions extracted with formic acid

Summary Extraction of a calcareous meadow soil with boiling formic acid containing 10 per cent acetylacetone yielded a fraction of soil organic matter representing about 40 per cent of the total. This fraction contained only 2.2 per cent N. Less than 18 per cent of this was mineralized during incubation for 8 weeks at 28°C. Further extraction of the soil with a formic acid and hydrofluoric acid mixture yielded a second fraction. This represented about 37 per cent of the total organic matter and contained 6.0 per cent N of which up to 41 per cent was mineralized during incubation. Preincubation and leaching had a stabilizing effect on subsequent mineralization of native N of a standard sandy loam soil.     

Effects of temperature on the growth of psychrophilic bacteria from glaciers.

Growth of five strains of psychrophilic bacteria (four Arthrobacter and one Pseudomonas) isolated from glacial deposits was studied at different temperatures. Three strains were facultative psychrophiles, having an optimum temperature for growth at about 25-28 degrees C and a maximum at about 32-34 degrees C. The two Arthrobacter glacialis strains were found to be obligate psychrophiles with an optimum at 13-15 degrees C and a maximum at 18 degrees C. Arrhenius plots showed that A. glacialis could compete with the facultative psychrophilic bacteria only at 0 degrees C, that is, the temperature of its natural environment. The psychrophilic Arthrobacter species studied here are more resistant to thermal stress than are marine psychrophilic bacteria. For Arthrobacter, in contrast to Pseudomonas, temperatures above the optimum induced formation of filaments and abnormal cells. The culture turbidity increased 10 to 30 times, whereas viable count tended to decrease. The thermal block seems to prevent cell wall synthesis and septation, but at a different step for each species.     

Effect of varying static and changing moisture levels during incubation on extractability of soil phosphate

Summary A sandy loam (pH 6.5) was incubated at 28°C at static moisture levels, ranging from 10 per cent saturation to 133 per cent saturation (waterlogging), for 6 and 12 weeks; other samples covering the same moisture range were first incubated for 6 weeks, and after changing all moisture levels to 50 per cent saturation were incubated for a further 6 weeks.With increasing static soil moisture level during incubation there was a slight reduction in Morgan-extractable phosphate up to 70 per cent saturation, but thereafter, due to anaerobic effects, there were considerable increases in extractable phosphate with increasing moisture level.With changing moisture level during incubation the effects of anaerobiosis became apparent where original moisture level was greater than 50 per cent saturation; extractable phosphate was reduced to levels lower than those occurring where the soil was maintained continuously at 50 per cent saturation. The extent of reduction in extractable phosphate increased with original soil saturation level.     

天山冻土产低温脂肪酶菌株的筛选及其多样性分析

【目的】通过天山冻土细菌的分离和产低温脂肪酶菌株的筛选,了解天山冻土微生物的物种多样性和产脂肪酶菌株的系统发育多样性,为高效低温脂肪酶生物技术奠定基础。【方法】采用稀浓度的R2A、TSB平板涂布分离天山冻土中可培养细菌,通过选择性培养基筛选产低温脂肪酶的菌株。采用细菌常规生理生化实验、最适生长温度、耐盐性、产酶性能对分离菌株的生理学进行研究,通过16S rRNA基因序列分析确定产脂肪酶菌种的系统进化地位,通过BOX-PCR指纹技术对16S rRNA基因高度同源性的菌株进一步区分。【结果】分离筛选到78株可培养低温菌,选择培养基显示有17株可产低温脂肪酶,其中8株在两种选择培养基中均可产脂肪酶和酯酶。17株产酶菌分别隶属于5个系统发育类群、6个属,其中假单胞菌属(Pseudomonas)占大多数(58.9%)。【结论】天山冻土中产低温脂肪酶的细菌具有较丰富的系统发育多样性,依据生长温度,均属于耐冷菌。     

Plasmid transfer in natural soil: a case by case study with nitrogen-fixing Enterobacter

Abstract In strains of nitrogen-fixing Enterobacter agglomerans , isolated from the rhizosphere of cereals, the nif genes are located on large plasmids. Plasmid pEA9 (200 kb) is self-transmissible between closely related strains. To collect data on possible uncontrolled gene spread, for planned releases of such bacteria, plasmid pEA9 was labelled with transposons (Tn 1725 and Tn 5 ) and used in mating experiments between homologous Enterobacter strains with soil as substrate. The soil was from a plot into which an actual release was being planned. In the majority of experiments it was not sterilized.
Survival and plasmid transfer is described, as are variations in temperature, time, moisture, pH and soil packing. Further experiments were with or without added energy sources, and with or without plant roots. Under standard conditions (22°C, pH 5.2, 15.5% moisture, loose soil, 2 × 10⁷ inoculated donor and recipient cells each per g soil, 3 days incubation) sterilized soil gave low rates of plasmid transfer (10⁻⁶ per donor) but non-sterilized soil gave none. Adding Luria broth or sucrose to non-sterilized soil elicited strong cell propagation, together with plasmid transfer (optimum after incubation for 1 day: 10⁻⁴ exconjugants per donor). No transfer could be registered in the presence of wheat seedling roots for periods up to 5 weeks.     

Characterization of 15 selected coccal bacteria isolated from antarctic rock and soil samples from the McMurdo-Dry Valleys (South-Victoria Land)

Summary Approximately 1500 cultures of microorganisms were isolated from rocks and soils of the Ross Desert (McMurdo-Dry Valleys). From these, 15 coccoid strains were chosen for more detailed investigation. They were characterized by morphological, physiological and chemotaxonomical properties. All isolates were Grampositive, catalase-positive and nonmotile. Six strains showed red pigmentation and could be identified as members of the genera Micrococcus (M. roseus, M. agilis) or Deinococcus. In spite of their coccoid morphology, the remaining nine strains had to be associated with coryneform bacteria (Arthrobacter, Brevibacterium), because of their cell wall composition and G+C ratios. Most of the strains were psychrotrophic, but one strain was even obligately psychrophilic, with a temperature maximum below 20°C. Red cocci had in vitro pH optima above 9.0 although they generally originated from acid samples. Most isolates showed a preference for sugar alcohols and organic acids, compounds which are commonly known to be released by lichens, molds and algae, the other components of the cryptoendolithic ecosystem. These properties indicate that our strains are autochthonous members of the natural Antarctic microbial population.     

Microbial communities and activities in alpine and subalpine soils

Soil samples were collected along two slopes (south and north) at subalpine (1500–1900 m, under closed vegetation, up to the forest line) and alpine altitudes (2300–2530, under scattered vegetation, above the forest line) in the Grossglockner mountain area (Austrian central Alps). Soils were analyzed for a number of properties, including physical and chemical soil properties, microbial activity and microbial communities that were investigated using culture-dependent (viable heterotrophic bacteria) and culture-independent methods (phospholipid fatty acid analysis, FISH). Alpine soils were characterized by significantly ( P <0.01) colder climate conditions, i.e. lower mean annual air and soil temperatures, more frost and ice days and higher precipitation, compared with subalpine soils. Microbial activity (soil dehydrogenase activity) decreased with altitude; however, dehydrogenase activity was better adapted to cold in alpine soils compared with subalpine soils, as shown by the lower apparent optimum temperature for activity (30 vs. 37 °C) and the significantly ( P <0.01–0.001) higher relative activity in the low-temperature range. With increasing altitude, i.e. in alpine soils, a significant ( P <0.05–0.01) increase in the relative amount of culturable psychrophilic heterotrophic bacteria, in the relative amount of the fungal population and in the relative amount of Gram-negative bacteria was found, which indicates shifts in microbial community composition with altitude.     

Influence of temperature on growth rate and competition between two psychrotolerant Antarctic bacteria: low temperature diminishes affinity for substrate uptake.

The growth kinetics of two psychrotolerant Antarctic bacteria, Hydrogenophaga pseudoflava CR3/2/10 (2/10) and Brevibacterium sp. strain CR3/1/15 (1/15), were examined over a range of temperatures in both batch culture and glycerol-limited chemostat cultures. The maximum specific growth rate (mu max) and Ks values for both bacteria were functions of temperature, although the cell yields were relatively constant with respect to temperature. The mu max values of both strains increased up to an optimum temperature, 24 degrees C for 2/10 and 20 degrees C for 1/15. Strain 1/15 might therefore be considered to be more psychrophilic than strain 2/10. For both bacteria, the specific affinity (mu max/Ks) for glycerol uptake was lower at 2 than at 16 degrees C, indicating a greater tendency to substrate limitation at low temperature. As the temperature increased from 2 to 16 degrees C, the specific affinity of 1/15 for glycerol increased more rapidly than it did for 2/10. Thus 1/15, on the basis of this criterion, was less psychrophilic than was 2/10. The steady-state growth kinetics of the two strains at 2 and 16 degrees C imply that 1/15 would be able to outgrow 2/10 only at relatively low substrate concentrations (< 0.32 g of glycerol.liter-1) and high temperatures (> 12 degrees C), which suggests that 1/15 has a less psychrotolerant survival strategy than does 2/10. Our data were compared with other data in the literature for bacteria growing at low temperatures. They also showed an increase of substrate-specific affinity with increasing temperature.(ABSTRACT TRUNCATED AT 250 WORDS)     

SOME BIOCHEMICAL CHARACTERISTICS OF FRESHLY ISOLATED STRAINS OF THE GENUS SERRATIA

SUMMARY: Many of 110 strains of Serratia , isolated from soil, water, milk and dairy equipment, were biochemically closely related to the coli-aerogenes bacteria. Acid and gas was formed from glucose in 14 days at 30° by 53% and from lactose and MacConkey's broth by about 40%. All except one strain gave——++ IMViC reactions.
An inverse relationship was observed between depth of pigmentation and carbohydrate fermentation. Complete loss of pigment in mutant strains was not uncommon, and was associated with loss of proteolytic properties and increase of saccharolytic activity.
The majority of the strains had psychrophilic characteristics: 75% grew at 3–5°. Most strains showed moderate growth at 37°, but only 7 formed red pigment at that temperature.
All strains resembled Serratia marcescens in morphology, containing minute coccoid rods smaller than those of coli-aerogenes bacteria.