Bacillus cereus biol 2402

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Classification

Domain: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Bacillales
Family: Bacillaceae

Species

Genus: Bacillus
Species Group: Bacillus cereus group

NCBI: Taxonomy

Habitat Information

The dirt sample that the B. cereus came from was collected on September 3, 2015 in Lakeway, Texas. The dirt was in a shady area underneath some trees between a creek and a small field. It was 91 degrees Fahrenheit, 44% humidity, and had not rained in the past 24 hours. The dirt was collected from about 2 inches below the surface. Approximate grid coordinates from the NRCS soil map are 3359230 x 598060. Soil type according to the NRCS soil map is volente silty clay loam, 1 to 8% slopes.

Description and Significance

Colony Appearance: Matte, white, flat colonies with irregular to lobate margins.
Cellular Appearance: Rod-shaped, endospore forming, and Gram-positive.

Significance in Medical and Veterinary Practices
B. cereus is predominantly linked to common infectious diseases seen in humans and animals. This organism can be found in high numbers in natural, domestic, and medical environments and thus is a common contaminant [1]. Because B. cereus has resistant endospores, they are able to survive many processes (ex: heat and drying) related to food production and subsequently end up in food products [2]. In regards to food-poisoning, B. cereus produces two types of endotoxins, one is linked to diarrheal illness and the other is linked to vomiting [3]. Aside from food-poisoning, B.cereus can also be responsible for severe infections in the eye, respiratory-tract, and the central nervous system [1]. The knowledge of characteristics associated with B. cereus infections is extremely important in medical practice. For example, B.cereus is often the primary pathogen behind ocular infections [1]. Endophthalmitis, which affects the intraocular cavities, is a serious inflammation that can lead to visual impairment within 12-48 hours after infected [1,4]. In this case, quick diagnosis is necessary to prevent any unrepairable deterioration of an infected eye [1].

Possible Antimicrobial Activity
Based on the microbiological study of 89 strains of Bacillus species isolated from clinical blood cultures done by Carmelita U. Tuazon, M.D., MPh, all strains of B. cereus was found to be [5]

susceptible to:

• imipenem
• vancomycin
• chloramphenicol
• gentamicin
• ciprofloxacin
  

resistant to:

• all penicillins
• oxacillin
• cephalosporins with the exception of mezlocillin
  

In Lab: We tested our sample of B. cereus for antimicrobial sensitivity with bacitracin, optochin, nafcillin, novobiocin, cefoxitin, and oxacillin. Of all of those, only novobiocin was a successful antimicrobial and produced a zone of inhibition. We also tested four disinfectants, 70% isopropyl alcohol, 10% bleach, orange, and 100% lysol. Lysol was the only disinfectant that produced a zone of inhibition.

Genome Structure

GENOME OVERVIEW
The chromosome of B. cereus is circular with about 5,411,809 nucleotides [7].
The following make up the genomic structure of B. cereus [7]:

• 5481 genes
• 5234 protein coding genes
• 147 structural RNAs
• 5, 366 RNA operons

S RIBOSOMAL SEQUENCE
Through PCR, we determined that our soil organism's S Ribosomal sequence is:

Forward sequence:

 ACGGAGCACGCCGCGTGAGTGATGAAGGCTTTCGGGT
 CGTAAAACTCTGTTGTTAGGGAAGAACAAGTGCTAGTTGAATAAGCTGGCACCTTGACGGTACCTAACCAGAAAGCCACG
 GCTAACTACGTGCCAGCAGCCGCGGTAATACGTAGGTGGCAAGCGTTATCCGGAATTATTGGGCGTAAAGCGCGCGCAGG
 TGGTTTCTTAAGTCTGATGTGAAAGCCCACGGCTCAACCGTGGAGGGTCATTGGAAACTGGGAGACTTGAGTGCAGAAGA
 GGAAAGTGGAATTCCATGTGTAGCGGTGAAATGCGTAGAGATATGGAGGAACACCAGTGGCGAAGGCGACTTTCTGGTCT
 GTAACTGACACTGAGGCGCGAAAGCGTGGGGAGCAAACAGGATTAGATACCCTGGTAGTCCACGCCGTAAACGATGAGTG
 CTAAGTGTTAGAGGGTTTCCGCCCTTTAGTGCTGAAGTTAACGCATTAAGCACTCCGCCTGGGGAGTACGGCCGCAAGGC
 TGAAACTCAAAGGAATTGACGGGGGCCCGCACAAGCGGTGGAGCATGTGGTTTAATTCGAAGCAACGCGAAGAACCTTAC
 CAGGTCTTGACATCCTCTGAAAACCCTAGAGATAGGGCTTCTCCTTCGGGAGCAGAGTGACAGGTGGTGCATGGTTGTCG
 TCAGCTCGTGCCGTGAGATGTCATANNNTNGTTTTCC

Reverse Sequence:

 ACCTGTCACTCTGCTCCCGAAGGAGAAGCCCTATCTCTAGGGTTTTCAGAGGATGTCAAGACCTGG
 TAAGGTTCTTCGCGTTGCTTCGAATTAAACCACATGCTCCACCGCTTGTGCGGGCCCCCGTCAATTCCTTTGAGTTTCAG
 CCTTGCGGCCGTACTCCCCAGGCGGAGTGCTTAATGCGTTAACTTCAGCACTAAAGGGCGGAAACCCTCTAACACTTAGC
 ACTCATCGTTTACGGCGTGGACTACCAGGGTATCTAATCCTGTTTGCTCCCCACGCTTTCGCGCCTCAGTGTCAGTTACA
 GACCAGAAAGTCGCCTTCGCCACTGGTGTTCCTCCATATCTCTACGCATTTCACCGCTACACATGGAATTCCACTTTCCT
 CTTCTGCACTCAAGTCTCCCAGTTTCCAATGACCCTCCACGGTTGAGCCGTGGGCTTTCACATCAGACTTAAGAAACCAC
 CTGCGCGCGCTTTACGCCCAATAATTCCGGATAACGCTTGCCACCTACGTATTACCGCGGCTGCTGGCACGTAGTTAGCC
 GTGGCTTTCTGGTTAGGTACCGTCAAGGTGCCAGCTTATTCAACTAGCACTTGTTCTTCCCTAACAACAGAGTTTTACGA
 CCCGAAAGCCTTCATCACTCACGCGGCGTTGCTCCGTCAGACTTTCGTCCATTGCGGAAGATTCCCTACTGCTGCCNCNC
 GTANAGTACTGG

Cell Structure, Metabolism and Life Cycle

Cell Structure: Bacillus cereus is a rod shaped, Gram- positive bacterium. Its cell structure consists of an inner membrane and a thick peptidoglycan which functions to maintain cell shape [9]. Clinical isolates of B. cereus have a glycoprotein S-layer over its peptidoglycan. The S-layer is involved in the virulence of B. cereus by enablling it to adhere to laminin, type I collagen, fibronectin, and fibrinogen of the epithelium, and thus has a role in increasing interaction between B.cereus and its host[10]

Life Cycle: B. cereus is widely reported as a soil bacterium and also occurs in the rhizosphere of some plants. Some strains of B. cereus produce antibiotics able to suppress fungal diseases of the rhizosphere. B. cereus is also a food poisoning bacterium that can occasionally be an opportunistic human pathogen[8]. B. cereus spores germinate within an insect or animal host or on contact with organic matter, entering the soil via the droppings of an animal host or upon the host's death. Saprophytic growth in soil, including transition from a single cell to a multicellular form, then ensues. Cells and spores may then contaminate plant material and enter food processing areas. B. cereus spores resist extreme environmental conditions including heat, freezing, drying, and radiation. The hydrophobic spore surface allows attachment to food and processing equipment, where biofilm formation may further protect forms of the organism[12]

Metabolism: B. cereus is a facultative aerobe so it can utilize oxygen as a terminal electron accepter, but also has methods of anaerobic respiration as a mechanism of energy release. Studies show that B. cereus has metabolic enzymes such as NADH dehydrogenases, succinate dehydrogenase, complex III, non-proton-pumping cytochrome bd quinol oxidases, and proton-pumping oxidases such as cytochrome c oxidase and cytochrome aa3 quinol oxidase [11].

Physiology and Pathogenesis

OVERVIEW
B. Cereus is motile, catalase positive, able to ferment glucose, unable to ferment lactose, able to reduce nitrate to non gaseous nitrogenous compounds, produces amylase, and has alpha hemolytic activity.

While B. cereus is associated mainly with food poisoning, it is being increasingly reported to be a cause of serious and potentially fatal non-gastrointestinal-tract infections.The pathogenicity of B. cereus, whether intestinal or nonintestinal, is intimately associated with the production of tissue-destructive exoenzymes. Among these secreted toxins are four hemolysins, three distinct phospholipases, an emesis-inducing toxin, and proteases. [6].

BIOCHEMICAL TEST RESULTS

• Phenol Red Broth: glucose: positive; lactose: degradation of peptone, alkaline end products; sucrose: degradation of peptone, alkaline end products
• Starch Hydrolysis: positive
• Casein Hydrolysis: slight positive
• Gelatin Hydrolysis: positive
• DNA Hydrolysis: negative
• Lipid Hydrolysis: negative
• Methyl Red: negative
• Voges Proskauer: negative
• Citrate Test: negative
• SIM Tests: negative for sulfur reduction, positive for motility
• Nitrate Reduction: organism reduced nitrate to nongaseous nitrogenous compounds
• Urea Hydrolysis: negative
• Triple Sugar Iron Agar: negative for fermentation and sulfur reduction; peptone was catabolized aerobically with alkaline products

(Some results may be inaccurate due to lab or human error)

References

[1] Logan, A. 1988. Bacillus species of medical and veterinary importance. J. Med. Microbiol., 157-165. <http://jmm.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-25-3-157?crawler=true&mimetype=application/pdf>

[2] Rosenquist, H. et al. 2005. Occurrence and significance of Bacillus cereus and Bacillus thuringiensis in ready-to-eat food. FEMS Microbiology Letters.

[3] Department of Public Health, Division of Disease Control. "Foodborne Toxins–Toxins Produced by Bacteria Toxins Produced by Bacteria Toxins Produced by Bacteria ". Accessed December 3, 2015. <http://www.phila.gov/health/pdfs/diseases/FoodborneToxins_Bacteria_FAQ_2011.pdf>

[4] Egan, D. (2015). Endophthalmitis. MedScape. Accessed December 3, 2015. <http://emedicine.medscape.com/article/799431-overview>

[5] Tuazon, C. "Bacillus species". antimicrobe site. Acessed December 3, 2015. <http://www.antimicrobe.org/b82.asp>

[6] Bottone, E. (2010). Bacillus cereus, a Volatile Human Pathogen. CMR, 382-398. doi:10.1128

[7] "Bacillus cereus". MicrobeWiki site. Accessed December 3, 2015. <https://microbewiki.kenyon.edu/index.php/Bacillus_cereus>

[8]"Analysis of the Life Cycle of the Soil Saprophyte Bacillus cereus in Liquid Soil Extract and in Soil" NCBI website. Accessed November 22, 2015

[9] Ticknor, O., Kolsto, A., Hill, K., Keim. P., Laker, M., Tonks, M., and Jackson, P. “Fluorescent Amplified Fragment Length Polymorphism Analysis of Norwegian Bacillus cereus and Bacillus thuringiensis Soil Isolates.” Applied Environmental Microbiology. 2001. Volume 67(10). p. 4863–4873.

[10]Mignot, T., Denis, B., Couture-Tosi, E., Kolsto, A., Mock, M., Fouet, A. “Distribution of S-layers on the surface of Bacillus cereus strains: phylogenetic origin and ecological pressure.” Environmental Microbiology. 2001. Volume 3(8). p. 493–501.

[11]Duport, C., Zigha, A., Rosenfeld, E., and Schmitt, P. “Control of Enterotoxin Gene Expression in Bacillus cereus F4430/73 Involves the Redox-Sensitive ResDE Signal Transduction System.” Journal of Bacteriology. 2006. Volume 188. p. 6640–6651.

[12] Baumgardner, D. " Soil-Related Bacterial and Fungal Infections" Journal of the American Board of Family Medicine. 2012. Volume 25(5). p. 734-744

Author

Page authored by Zaneta Wu and Desiree Weinstock, students of Prof. Kristine Hollingsworth at Austin Community College.