Microorganisms, such as bacteriums, Fungis, algae, Protozoa and other beings, within assorted communities can be found in dirt, and they interact with each other in assorted ways ( Singleton 1992 ) . Microorganisms play an indispensable portion in biochemical procedures that recycle S, N, and C and in keeping dirt productiveness. They break down organic compounds to inorganic compounds, which can be used as foods by workss, therefore functioning as nexus between animate beings and workss ( Singleton 1992 ) . Bacteria compose the bulk of microbic population in dirt ; species of Bacillus, Clostridium, Arthrobacter, Pseudomonas, Rhizobium, Azotobacter, and Nitrobacter are by and large present ( Pelczar 1993 ) . Other micro-organisms such as Fungis exist copiously near the dirt surface where O is readily available ( Pelczar 1993 ) . Due to their part to dirty construction formation ; decomposition of organic affair ; toxin remotion ; and the biochemical cycling of C, N, phosphoric, and S, micro-organisms are important in keeping the dirt map, and besides, their extent of diverseness is critical to the care of dirt wellness and quality ( Pelczar 1993 ) . The figure and sorts of micro-organisms are affected by the presence of roots and the extent of the root system in dirt. Our aim is to insulate and place a pure civilization of dirt bacteria from a assorted population of dirt micro-organisms ( Pelczar 1993 ) .


To get down with, we cultured the assorted populations of aerophilic and anaerobiotic micro-organism from an agricultural dirt sample. First, a series of consecutive dilution were prepared from an agricultural dirt sample and they are 10-2, 10-3, 10-4, 10-5,10 -6,10 -7. Four pour home bases were prepared by pipetting inoculant from the 10-4,1 0-5, 10-6, 10-7 dilutions of the agricultural dirt sample, and were incubated at 22 oC for 48 hours, and were so placed in the electric refrigerator ( 4oC ) . In order to obtain the pure civilization of the dirt bacterium from the assorted populations, the run home base subculture was prepared from one of the settlements in the pour home base. And gram-staining was performed for the bacteria. Bacterial settlement morphology was recorded and cellular agreement was examined utilizing compound microscope. Biochemical activities of the dirt bacterial isolate in the cycling of C, N and S were tested ; those activities include starch hydrolysis, H2S production, motility, ammonification, nitrification, denitrification, O tolerance and catalase production. To analyze the environmental factors, such as temperature, PH and osmotic force per unit area, on the growing of the bacterial isolate, the isolate was tested at 4, 22, 37 and 50 oC ; at pH 3, 5, 7 and 9 ; and at different concentrations of salt ( 0, 0.5, 2, and 5 % NaCL ) under incubation for one hebdomad ( Robertson and Egger 2010 ) .


The strain we studied was isolated from the pour plates incubated at 22 oC. The isolate was Gram positive, facultative anaerobic, catalase positive, motile rods with whiplike beings. Our strain produced level, filiform, unsmooth, rhizoid settlements with a diameter of 15mm, and they are dull, opaque and white. The cells are bacillar and are arranged as a individual B with a dimension of 4um*1um ( table 1 ) . It was tested positive for starch hydrolysis, ammonification, denitrification ( NO3- to NO2- ) , nitrification ( NH4+ to NO2- ) and catalase production ( table 1 ) . It showed a broad growing temperature scope from 4 to 50oC, with an optimum temperature of 37 oC, and it had a PH growing scope from PH 3 to PH 9 with an optimum Ph of 7, but there was no growing at PH5 ( table 1 ) . It tolerated salt concentration from 0 % to 5 % , and grew best at 0.5 % and was inhibited by high concentration of salt in the medium ( table 1 ) .

Table 1. Main features of the strain we studied.


Temperature scope

4-50 oC

Optimum temperature

37 oC

PH scope


% NaCL scope

0 % -5 %

Cell dimensions ( um )


Ironss of cells


Colony diameter ( millimeter )

15 millimeter

Gram discoloration


Starch hydrolysis


H2S decrease






Indole production


Denitrification ( NO3- to NO2- )


Denitrification ( NH4+ to N2 )


Nitrification ( NH4+ to NO2- )


Nitrification ( NO2- to NO3- )



Our isolate was identified as strains of Bacillus species. Their colonial and microscopic morphologies and biochemical trial profiles were typical for these species. The cells of genus Bacillus are bacillar and may happen singly or in ironss ( Goodfellow et al, 1998 ) , compared to our observation that the cells were bacillar and were arranged as a individual B. The rods may be rather little ( 0.5*1.2um ) or instead big ( 2.5*10 um ) ( Goodfellow et al, 1998 ) , and our mensural dimension of the rods is about 1*4 um, which is within the above scope. Our consequence indicates the production of catalase, which matches the profile of genus Bacillus that most species produce catalase ( Goodfellow et al, 1998 ) . Most Bacillus species are motile by agencies of scourge ( Egger and Robertson 2010 ) and our trial showed the indicant of motility. The cells can be Gram-positive or negative or positive merely in the early phase of growing ( Goodfellow et al, 1998 ) , and our trial suggests that the cell is Gram-positive. Cell morphology of Bacillus strains varies greatly with environmental factors, including composing of medium, temperature of vaccination, humidness ; nevertheless, our strain has as the same signifier of rhizoid as Bacillus mycoides ( Goodfellow et al, 1998 ) . Colonies of pure civilization can be semitransparent or opaque, milky or creamy-colored in a individual home base, related to the denseness of endospores within the settlements ( Goodfellow et al, 1998 ) , while our strain is opaque and white. Strains of Our stray bacteriums were facultively anaerobiotic while the published information suggest that they can be aerophilic or facultively anaerobiotic. Endospores are formed by Bacillus species in unfavourable environment ( Goodfellow et al, 1998 ) . The imperviable coat that surrounds the endospore can forestall it from inauspicious environment such as inordinate heat, stop deading and dehydration, so they can be hibernating in nature for a long period of clip

( Robertson and Egger 2010 ) . Endospore construction can be confirmed by subjecting it to temperature of 70-80C for 10min and cultivate it under appropriate status ( Goodfellow et al, 1998 ) . The signifier of endospores is characteristic characteristics of Bacillus species ; it is normally cylindrical, or ellipsoidal or ellipse or unit of ammunition ( Goodfellow et al, 1998 ) . However, it should be noticed that endospores can non be formed under all cultural conditions, and therefore nonsporulating Bacillus species may be misidentified for other genera. Biochemical reactions such as denitrification, nitrification, ammonification and amylum hydrolysis were detected ( Goodfellow et al, 1998 ) . Denitrification is common among Bacillus species, during which nitrate is used as a terminal negatron acceptor during respiration and nitrite is generated ( Goodfellow et al, 1998 ) .Our consequence confirmed reaction because nitrate was reduced to nitrite with no farther decrease. Bacillus species are ammonifiers, capable of transforming N incorporating organic compounds, such as proteins, to ammonia ( Egger and Robertson 2010 ) . Our isolate carried out ammonification since ammonium hydroxide was detected. Our consequence shows that amylum was consumed by our bacteriums, utilizing amylum as their C beginning, and it matches McSpaddenaa‚¬a„?s consequence ( 2004 ) . All the strains of Bacillus species tested in McSpaddenaa‚¬a„?s experiment gave negative consequences in indole and H2S production trials, matching to our consequences that Indole and H2S were non produced ( 2004 ) . Bacillus species can turn at both low and high temperature ( Goodfellow et al, 1998 ) ; our consequence shows that our bacteriums can turn at temperature runing between 4 and 50 oC, with an optimum temperature of 37 oC. Their ability to defy high temperature can be attributed to the growing of endospores when returned to an optimum temperature ( Goodfellow et al, 1998 ) . Our bacteriums can turn at PH from 3 to 9, with an optimum PH of 7, but can non turn at 5, compared to the published informations which suggest that Bacillus species can turn at low and high PHs ( Goodfellow et al, 1998 ) . The fact that there was no growing at PH 5 can be attributed to mistakes made during our experiment. When we were utilizing the sterile technique to inoculate the agar plates ; cells could be killed before incubation due to the violent death of inoculant by the het cringle. Some strains of Bacillus species are salt tolerant, some can merely turn under solution with certain salt concentration ( Goodfellow et al, 1998 ) .Our bacteriums have broad growing scope of salt concentration, with an optimum concentration of 5.

In order to find the scope of growing temperatures, growing of civilization was observed at 50 oC and 65 oC after 24h of incubation, at 37 oC after 2 yearss, and at 15oC after 14 yearss ( Llarch et al. 1996 ) . Alternatively of detecting the growing of the civilization one hebdomad after incubation, we can better our experiment by detecting civilizations that grow at different temperatures after different period clip of incubation.

Use of organic acids such as citrate and propionate can be tested by inoculating angles of citrate and propionate use medium, and incubating them for 14 yearss. A ruddy colour indicates use of organic acids. Production of dihydroxyacetone can be tested by inoculating home bases of tyrosine agar with one run of inoculant and incubate them, glade of the tyrosine crystals around and below the growing gives a positive consequence ( Goodfellow et al, 1998 ) .

Bacillus species play a critical function in the biological cycling of C and N due to their ability to degrade a series of biopolymers ( Goodfellow et al, 1998 ) . Besides, Bacillus species can advance harvest wellness and productiveness by stamp downing works pathogens and plagues, and their utilizations in agribusiness are being exploited. Some strains of Bacillus species have been developed as biological antifungals, insect powders, and nematicides or generic works growing boosters ( McSpadden 2004 ) . Our aims were achieved as we isolated our bacteriums and identified them as Bacillus species.


Goodfellow, M. , Williams, S.T. , Mordarski M.. 1998. Bergeyaa‚¬a„?s Manual of Systematic Bacteriology, Volumn 2. Springer, NY, pp. 1104-25.

Llarch, A. , Logan, N.A. , Castellvi, J. , Prieto, M.J. , Guinea, J.. 1996. Isolation and Characterization of Thermophilic Bacillus spp.from Geothermal Environments on Deception Island, South Shetland Archipelago.Microb Ecol. 34:58-65.

McSpadden, G.B.. 2004. Ecology of Bacillus and Paenibacillus

spp. in agricultural systems. Phytopathology 94:1252-1258.

Pelczar, M.J.. 1993. Microbiology — constructs and applications. McGraw-Hill, NY, pp. 77-83.

Robertson, S and Egger, K. 2010. BIOL 203 Microbiology Laboratory Manual. UNBC.

Singleton, Paul. 1992. Introduction to bacteriums: for pupils of biological science, biotechnology & A ; medicine / Paul Singleton. Chichester, NY, pp. 144-9.

( Robertson and Egger 2010 )